Questions and Answers
What causes pre-tibial mixed edema?
Periorbital edema is caused by the accumulation of glycosaminoglycans around the eyes.
True
Name one primary cause of hypothyroidism.
Hashimoto's thyroiditis
Low thyroid hormone leads to decreased degradation of __________, resulting in edema.
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Match the following conditions with their characteristics:
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Which of the following tests is crucial for assessing causes of hypothyroidism?
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Carpal tunnel syndrome can develop from edema around the ulnar nerve.
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What type of hypothyroidism shows low free T4 and high TSH?
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An MRI can help identify lesions in the __________ or pituitary affecting hormone production.
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What is a common medication that can cause drug-induced hypothyroidism?
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What genetic alleles have been linked to thyroid health susceptibility?
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Postpartum thyroiditis only occurs in females one year after giving birth.
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Name one medication that can cause drug-induced hypothyroidism.
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Hypothyroidism can result from both iodine deficiency and _______.
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Match the type of thyroiditis with its description:
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Which symptom is commonly associated with hypothyroidism?
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Congenital hypothyroidism can arise from maternal antibody-mediated destruction of the infant's thyroid gland.
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What is one of the common effects of hypothyroidism on the reproductive system?
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Increased _______ due to hypothyroidism can lead to cold intolerance.
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Which symptom is classified under the seven 'P' mnemonic for congenital hypothyroidism?
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What hormone does the anterior pituitary secrete in response to TRH?
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T4 is the only thyroid hormone produced by the thyroid gland.
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What is the role of D-iodinases in thyroid hormone physiology?
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The conversion of glucose to pyruvate is known as __________.
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Match the effects of thyroid hormones with their corresponding systems:
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Which of the following is a metabolic effect of thyroid hormone?
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Hashimoto's Thyroiditis is an autoimmune condition that primarily affects males.
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What is the primary cause of primary hypothyroidism?
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The thyroid hormone primarily responsible for increasing metabolism is __________.
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Which of the following systems does thyroid hormone NOT primarily affect?
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What is the primary thyroid hormone released by the thyroid gland?
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Triiodothyronine (T3) is produced more than thyroxine (T4).
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What enzyme converts T4 to T3 inside cells?
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Thyroid hormones stimulate __________ synthesis, increasing ATP consumption.
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Match the system to its effect influenced by thyroid hormones:
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What is the effect of thyroid hormones on the muscular system?
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Hashimoto's Thyroiditis is more common in males than females.
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What does TSH stimulate the thyroid gland to produce?
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Thyroid hormones enhance __________ activity, which affects metabolic processes.
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What is one of the common causes of primary hypothyroidism?
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What is a common characteristic of Subacute Granulomatous Thyroiditis?
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Iodine excess can lead to decreased production of thyroid hormones.
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What is the primary consequence of Hashimoto's Thyroiditis?
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Hypothyroidism may lead to an increase in _______ levels due to decreased LDL receptor activity.
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Match the type of hypothyroidism with its cause:
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What causes carpal tunnel syndrome in the context of hypothyroidism?
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Which of the following symptoms is commonly associated with hypothyroidism?
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Primary hypothyroidism is characterized by high free T4 levels.
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Identify one main characteristic of Hashimoto's thyroiditis.
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Reidel's Thyroiditis can often be associated with autoimmune pancreatitis.
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Pre-tibial mixed edema is due to the accumulation of __________ in the dermis.
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Name one of the seven 'P' symptoms of congenital hypothyroidism.
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Match the type of hypothyroidism with its description:
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High levels of TSH and prolactin can inhibit production of _______ and _______.
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What role does thyroid hormone play in lipid metabolism?
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Which of the following laboratory results indicates central hypothyroidism?
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MRI can be used to identify lesions affecting thyroid hormone production.
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Name one medication that can lead to drug-induced hypothyroidism.
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Glycosaminoglycans accumulation can lead to ____________, causing swelling in various body parts.
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Which type of hypothyroidism occurs due to the destruction of thyroid tissue by immune cells?
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Which of the following autoimmune diseases is commonly associated with thyroid peroxidase and thyroglobulin targeting leading to gland destruction?
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Reidel's thyroiditis is primarily characterized by the presence of IgM antibodies.
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What is the primary cause of postpartum thyroiditis?
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Congenital hypothyroidism can be caused by maternal antibody-mediated destruction or developmental issues like __________.
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Match the following types of thyroiditis with their characteristics:
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What condition results from acute hormone disruption due to thyroid gland damage?
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Increased LDL cholesterol levels in hypothyroidism result from decreased receptor activity in the liver.
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Name one medication that can cause drug-induced hypothyroidism.
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Elevated levels of __________ can lead to infertility and menstrual irregularities in females with hypothyroidism.
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Which symptom is least likely to be associated with hypothyroidism?
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Which hormone primarily stimulates the thyroid gland to produce thyroid hormones?
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Thyroxine (T4) accounts for 10% of the thyroid hormones produced by the thyroid gland.
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What is the primary active form of thyroid hormone that binds to intracellular receptors?
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The enzyme _______ converts T4 to active T3 inside cells.
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Match the following systems with their effects influenced by thyroid hormones:
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What effect do thyroid hormones have on the metabolism of lipids?
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Hypothyroidism can result from autoimmune conditions like Hashimoto's Thyroiditis.
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Which metabolic pathway involves the breakdown of glycogen to glucose?
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Thyroid hormones stimulate _______ consumption by enhancing sodium-potassium ATPase activity.
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Which of the following systems is most directly influenced by thyroid hormones in terms of calcium metabolism?
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What is a common outcome of low thyroid hormone levels?
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Periorbital edema is a consequence of GAG accumulation around the eyes.
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Name one test that is used to differentiate between primary and central causes of hypothyroidism.
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The accumulation of glycosaminoglycans can lead to __________ syndrome due to edema around the median nerve.
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Match the following conditions with their characteristics:
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Which hormone shows low levels in central causes of hypothyroidism?
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MRI is used to identify lesions in the thyroid gland.
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What autoimmune condition is characterized by fibrous tissue and may lead to hypothyroidism?
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Postpartum thyroiditis typically occurs __________ months after childbirth.
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What might lead to drug-induced hypothyroidism?
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Which process is NOT promoted by thyroid hormones?
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Thyroid hormones increase the activity of the sympathetic nervous system.
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What is the primary thyroid hormone that is converted from T4 into its active form?
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Thyroid hormones enhance metabolic functions by binding to __________ receptors.
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Match the system to its effect influenced by thyroid hormones:
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Which of the following is a characteristic of postpartum thyroiditis?
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Congenital hypothyroidism can arise from maternal antibody-mediated destruction of the infant's thyroid gland.
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What is the primary consequence of Hashimoto's thyroiditis?
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Iodine deficiency leads to decreased synthesis of functional thyroid hormone, prevalent in __________ areas worldwide.
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Match the type of thyroiditis with its characteristic:
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Study Notes
Thyroid Hormone Physiology
- The hypothalamus releases thyrotropin releasing hormone (TRH) which stimulates the anterior pituitary.
- Anterior pituitary secretes thyroid stimulating hormone (TSH) in response to TRH.
- TSH stimulates the thyroid gland to produce thyroid hormones, primarily thyroxine (T4, 90%) and triiodothyronine (T3, 10%).
- T4 is converted to active T3 inside cells via the enzyme D-iodinases.
- T3 binds to intracellular receptors, enhancing metabolic functions and gene expression.
Metabolic Effects of Thyroid Hormone
- Increases metabolism by promoting:
- Glycogenolysis: breakdown of glycogen to glucose.
- Glycolysis: conversion of glucose to pyruvate.
- Lipolysis: breakdown of lipids into fatty acids and glycerol.
- Stimulates sodium-potassium ATPase, increasing ATP consumption and requiring higher energy production.
Impact on Various Systems
-
Cardiovascular System:
- Enhances beta-adrenergic receptor sensitivity, increasing heart rate (chronotropic effect) and contractility (inotropic effect).
- Maintains vasomotor tone, balancing vasoconstriction and vasodilation.
-
Skeletal System:
- Regulates osteoclasts and osteoblasts, affecting bone remodeling and calcium metabolism.
-
Nervous System:
- Increases sympathetic nervous system activity.
-
Gastrointestinal System:
- Enhances GI motility and secretions.
-
Skin and Hair:
- Improves blood flow to skin, aiding the growth of hair, skin, and nails.
- Regulates activity of sebaceous and sweat glands.
-
Reproductive System:
- Supports development and function, influences sex hormone binding globulin and regulates LH and FSH levels.
-
Muscular System:
- Promotes muscle development and contraction by regulating calcium ATPases in muscle cells.
Primary Hypothyroidism
-
Common causes include antibodies against thyroid proteins, viral infections, and drug-induced damage.
-
Hashimoto's Thyroiditis:
- Autoimmune condition, more prevalent in females.
- Antibodies target thyroid peroxidase and thyroglobulin, leading to gland destruction via molecular mimicry.
- Genetic susceptibility linked to HLA-DR3 and HLA-DR5 alleles.
-
Postpartum Thyroiditis:
- Occurs in females within one year post-birth.
- Characterized by acute hypothyroidism due to antibody-mediated destruction, typically resolves over time.
-
Subacute Granulomatous Thyroiditis:
- Triggered by viral infections, causing thyroid inflammation.
- Symptoms include thyroid gland pain; may show elevated erythrocyte sedimentation rate (ESR) due to inflammation.
-
Drug-Induced Hypothyroidism:
- Caused by medications like amiodarone, lithium, and iodine-131, which damage thyroid tissue and hinder hormone production.
Pathophysiology and Symptoms
- As thyroid gland undergoes damage, thyroid hormones may initially spill into circulation causing transient hyperthyroidism.
- Over time, continued damage leads to decreased thyroid hormone levels, resulting in hypothyroidism symptoms such as fatigue, weight gain, and cold intolerance.### Hashimoto's Thyroiditis and Reidel's Thyroiditis
- Hashimoto's thyroiditis is commonly seen in autoimmune thyroid diseases.
- Reidel's thyroiditis is characterized by the production of IgG4 antibodies that activate fibroblasts, leading to fibrosis around the thyroid gland.
- One-third of patients with Reidel's thyroiditis may develop hypothyroidism due to significant fibrosis replacing normal thyroid tissue.
- Associated conditions include autoimmune pancreatitis, retroperitoneal fibrosis, and non-infectious aortitis.
Iodine Influence on Hypothyroidism
- Hypothyroidism can result from both iodine deficiency and excess.
- Iodine deficiency leads to decreased synthesis of functional thyroid hormone, prevalent in non-iodine fortified areas worldwide.
- High iodine levels can inhibit thyroid hormone synthesis through a mechanism known as the Wolf-Chaikoff effect, leading to decreased production of thyroid hormones T3 and T4.
Central Hypothyroidism Causes
- Central hypothyroidism can arise from hypothalamic or pituitary issues impacting TRH and TSH production.
- Hypothalamic dysfunction results in decreased TRH, leading to decreased TSH and thyroid hormone levels.
- Pituitary dysfunction, such as traumatic brain injury or tumors, may also hinder TSH production.
- Sheehan syndrome is a condition resulting from pituitary infarction due to severe postpartum hemorrhage, leading to reduced hormone production.
Congenital Hypothyroidism
- Congenital hypothyroidism can arise from maternal antibody-mediated destruction of the infant's thyroid gland or developmental issues like thyroid agenesis and dysgenesis.
- Dysfunction in the follicular cell enzyme thyroid peroxidase (TPO) hampers thyroid hormone production, leading to a condition known as dysgenetic goiter.
- Iodine deficiency is another significant cause of congenital hypothyroidism, impacting hormone production.
Clinical Features of Hypothyroidism
- Presence of goiter due to the accumulation of thyroglobulin when thyroid hormone is not adequately released.
- Patients may experience weight gain from reduced metabolic activity and appetite changes.
- Decreased body temperature resulting from lower heat production due to diminished metabolic processes, leading to cold intolerance.
- Bradycardia may occur from decreased beta-adrenergic receptor sensitivity and reduced heart rate.
- Hypertension can also be seen, despite hypothyroidism typically leading to decreased blood pressure, due to increased vasoconstriction.
- Bone growth and maturation are compromised, leading to potential short stature due to insufficient thyroid hormone.
- Neurological effects may include depression, fatigue, memory deficits, and decreased reflex responses from reduced sympathetic nervous system activity.
Seven 'P' Mnemonic for Congenital Hypothyroidism Symptoms
- Pot belly
- Pale skin
- Puffy face
- Protruding tongue
- Protruding umbilicus
- Poor brain development
- Prolonged neonatal jaundice### Deep Tendon Reflexes and Myopathy
- Hypothyroidism leads to delayed deep tendon reflexes, known as Wolffian sign.
- Muscle contraction, growth, and regeneration are impaired due to low thyroid hormone levels.
- Myopathy can develop, increasing creatinine kinase levels when muscle tissue is damaged.
- Weakness primarily affects proximal muscle groups, such as shoulders and hips.
Gastrointestinal Effects
- Hypothyroidism decreases GI motility and secretions, leading to constipation.
- Reduced motility causes more water and electrolytes to be absorbed, resulting in hard stools.
- Constipation can lead to complications like hemorrhoids.
Skin, Hair, and Nails Changes
- Decreased blood flow results in hair loss, especially on the outer third of the eyebrows (Queen's sign).
- Nails become brittle and thin due to insufficient blood supply.
- Skin appears dry and pale from decreased secretions and blood flow; decreased sebum production also contributes to dryness.
Liver Function and Lipid Metabolism
- Thyroid hormones maintain LDL and triglyceride receptor activity in the liver.
- Low thyroid hormone results in decreased LDL receptors, leading to increased levels of LDL and triglycerides in the blood, causing hypercholesterolemia and hypertriglyceridemia.
Reproductive System Effects
- Hypothyroidism causes hyperprolactinemia, which affects sex hormone production.
- Elevated TSH and prolactin inhibit FSH and LH production, leading to testosterone and estrogen deficiencies.
- Male symptoms include decreased sperm production, lower libido, gynecomastia, and potential erectile dysfunction.
- Female symptoms include decreased estrogen, impacting ovulation, menstrual cycles, and potentially causing infertility, oligomenorrhea, or amenorrhea.
- Increased prolactin can lead to galactorrhea (milk leakage) in females.
Edema and Connective Tissue Changes
- Low thyroid hormone leads to decreased degradation of glycosaminoglycans (GAGs), resulting in GAG accumulation and edema.
- Pre-tibial mixed edema occurs due to GAG accumulation in the dermis.
- Periorbital edema arises from GAG accumulation around the eyes.
- Carpal tunnel syndrome can develop from edema around the median nerve due to GAG buildup.
Diagnostic Approach to Hypothyroidism
- Differentiation between primary and central causes is key.
- Thyroid function tests assess free T4 and TSH levels to help establish the type of hypothyroidism.
- Primary hypothyroidism shows low free T4 and high TSH; central causes show low free T4 with either low TSH (pituitary issue) or low TRH (hypothalamic issue).
- MRI can help identify lesions in hypothalamus or pituitary affecting hormone production.
Primary Causes of Hypothyroidism
- Hashimoto's thyroiditis is characterized by positive TPO and thyroglobulin antibodies; definitive diagnosis may require biopsy.
- Postpartum thyroiditis occurs within a year of childbirth and is typically acute; antibodies may also be positive.
- Drug-induced hypothyroidism can stem from medications like amiodarone or lithium; patient history is crucial for identification.
- Renal thyroiditis can be challenging to diagnose and requires careful evaluation of fibrous tissue indicators.
Thyroid Hormone Physiology
- Hypothalamus secretes thyrotropin releasing hormone (TRH).
- TRH stimulates anterior pituitary to release thyroid stimulating hormone (TSH).
- TSH prompts thyroid gland to produce thyroxine (T4, 90%) and triiodothyronine (T3, 10%).
- T4 is converted to active T3 within cells by D-iodinases.
- T3 enhances metabolism and gene expression by binding to intracellular receptors.
Metabolic Effects of Thyroid Hormone
- Increases overall metabolism through:
- Glycogenolysis: breaking down glycogen to glucose.
- Glycolysis: converting glucose to pyruvate.
- Lipolysis: converting lipids into fatty acids and glycerol.
- Stimulates sodium-potassium ATPase, increasing ATP usage and energy production.
Impact on Various Systems
-
Cardiovascular:
- Enhances beta-adrenergic receptor sensitivity, increasing heart rate and contractility.
- Balances vasomotor tone between vasoconstriction and vasodilation.
-
Skeletal:
- Regulates osteoclasts and osteoblasts, affecting bone remodeling and calcium metabolism.
-
Nervous:
- Activates the sympathetic nervous system.
-
Gastrointestinal:
- Improves GI motility and secretion.
-
Skin and Hair:
- Increases blood flow to skin, promoting growth of hair and nails.
- Regulates function of sebaceous and sweat glands.
-
Reproductive:
- Assists in the regulation of sex hormone binding globulin and LH/FSH levels.
-
Muscular:
- Supports muscle development and contraction through calcium ATPase regulation.
Primary Hypothyroidism
- Common causes include thyroid antibodies, viral infections, and drug damage.
-
Hashimoto's Thyroiditis:
- Autoimmune condition mainly affecting females; antibodies target thyroid peroxidase and thyroglobulin.
- Associated with HLA-DR3 and HLA-DR5 allele susceptibility.
-
Postpartum Thyroiditis:
- Occurs within a year after childbirth, often resolves naturally.
-
Subacute Granulomatous Thyroiditis:
- Caused by viral infections leading to inflammation and elevated ESR.
-
Drug-Induced Hypothyroidism:
- Results from medications like amiodarone, lithium, and iodine-131 affecting hormone synthesis.
Pathophysiology and Symptoms
- Initial thyroid gland damage may cause transient hyperthyroidism.
- Prolonged damage results in hypothyroidism symptoms like fatigue, weight gain, and cold intolerance.
Hashimoto's vs. Reidel's Thyroiditis
- Hashimoto's is prevalent among autoimmune diseases.
- Reidel's thyroiditis involves IgG4 antibodies, leading to fibrosis and potentially hypothyroidism due to tissue replacement.
Iodine Influence on Hypothyroidism
- Both iodine deficiency and excess can result in hypothyroidism.
- Deficiency hinders functional thyroid hormone synthesis, more common in non-iodine fortified regions.
- Excess iodine can inhibit hormone production via the Wolf-Chaikoff effect.
Central Hypothyroidism Causes
- Arises from hypothalamic or pituitary issues affecting TRH and TSH production.
- Pituitary dysfunction may result from trauma or tumors, including Sheehan syndrome from postpartum hemorrhage.
Congenital Hypothyroidism
- Can occur due to maternal antibodies or developmental issues such as thyroid agenesis.
- Involves dysfunction of thyroid peroxidase, leading to dysgenetic goiter.
- Iodine deficiency is also a major contributor.
Clinical Features of Hypothyroidism
- Goiter may develop from thyroglobulin accumulation due to inadequate hormone release.
- Symptoms include weight gain, cold intolerance, bradycardia, hypertension, and neurological effects like depression and fatigue.
- Compromised bone growth may lead to short stature.
Seven 'P' Mnemonic for Congenital Hypothyroidism Symptoms
- Pot belly
- Pale skin
- Puffy face
- Protruding tongue
- Protruding umbilicus
- Poor brain development
- Prolonged neonatal jaundice
Deep Tendon Reflexes and Myopathy
- Hypothyroidism leads to delayed reflexes (Wolffian sign).
- Muscle contraction and growth hindered, possibly resulting in myopathy with elevated creatinine kinase.
Gastrointestinal Effects
- Hypothyroidism decreases GI motility, causing constipation and potential complications like hemorrhoids due to hard stools.
Skin, Hair, and Nails Changes
- Reduced blood flow leads to hair loss (Queen's sign) and brittle nails.
- Skin appears dry and pale due to decreased secretions and inadequate sebum production.
Liver Function and Lipid Metabolism
- Thyroid hormones regulate LDL and triglyceride receptor activity.
- Low thyroid hormone levels increase LDL and triglycerides, resulting in hypercholesterolemia and hypertriglyceridemia.
Reproductive System Effects
- Hyperprolactinemia from hypothyroidism interferes with sex hormone production.
- Male symptoms: decreased sperm production, low libido, gynecomastia, erectile dysfunction.
- Female symptoms: decreased estrogen, menstrual issues, and possible infertility; increased prolactin can cause galactorrhea.
Edema and Connective Tissue Changes
- Low thyroid hormone increases glycosaminoglycans (GAGs), leading to tissue edema.
- Pre-tibial and periorbital edema can occur from GAG accumulation, potentially causing carpal tunnel syndrome.
Diagnostic Approach to Hypothyroidism
- Differentiating primary from central causes via thyroid function tests for free T4 and TSH levels.
- Low free T4 and high TSH indicate primary hypothyroidism; low free T4 with low TSH indicates central issues.
- MRI helps identify hypothalamic or pituitary lesions.
Primary Causes of Hypothyroidism
- Hashimoto's thyroiditis: confirmed by positive TPO and thyroglobulin antibodies; biopsy may be needed.
- Postpartum thyroiditis manifests within a year of childbirth, typically acute.
- Drug-induced hypothyroidism requires careful patient history and identification of relevant medications.
- Diagnosing renal thyroiditis necessitates evaluating fibrous tissue indicators.
Thyroid Hormone Physiology
- Hypothalamus secretes thyrotropin releasing hormone (TRH).
- TRH stimulates anterior pituitary to release thyroid stimulating hormone (TSH).
- TSH prompts thyroid gland to produce thyroxine (T4, 90%) and triiodothyronine (T3, 10%).
- T4 is converted to active T3 within cells by D-iodinases.
- T3 enhances metabolism and gene expression by binding to intracellular receptors.
Metabolic Effects of Thyroid Hormone
- Increases overall metabolism through:
- Glycogenolysis: breaking down glycogen to glucose.
- Glycolysis: converting glucose to pyruvate.
- Lipolysis: converting lipids into fatty acids and glycerol.
- Stimulates sodium-potassium ATPase, increasing ATP usage and energy production.
Impact on Various Systems
-
Cardiovascular:
- Enhances beta-adrenergic receptor sensitivity, increasing heart rate and contractility.
- Balances vasomotor tone between vasoconstriction and vasodilation.
-
Skeletal:
- Regulates osteoclasts and osteoblasts, affecting bone remodeling and calcium metabolism.
-
Nervous:
- Activates the sympathetic nervous system.
-
Gastrointestinal:
- Improves GI motility and secretion.
-
Skin and Hair:
- Increases blood flow to skin, promoting growth of hair and nails.
- Regulates function of sebaceous and sweat glands.
-
Reproductive:
- Assists in the regulation of sex hormone binding globulin and LH/FSH levels.
-
Muscular:
- Supports muscle development and contraction through calcium ATPase regulation.
Primary Hypothyroidism
- Common causes include thyroid antibodies, viral infections, and drug damage.
-
Hashimoto's Thyroiditis:
- Autoimmune condition mainly affecting females; antibodies target thyroid peroxidase and thyroglobulin.
- Associated with HLA-DR3 and HLA-DR5 allele susceptibility.
-
Postpartum Thyroiditis:
- Occurs within a year after childbirth, often resolves naturally.
-
Subacute Granulomatous Thyroiditis:
- Caused by viral infections leading to inflammation and elevated ESR.
-
Drug-Induced Hypothyroidism:
- Results from medications like amiodarone, lithium, and iodine-131 affecting hormone synthesis.
Pathophysiology and Symptoms
- Initial thyroid gland damage may cause transient hyperthyroidism.
- Prolonged damage results in hypothyroidism symptoms like fatigue, weight gain, and cold intolerance.
Hashimoto's vs. Reidel's Thyroiditis
- Hashimoto's is prevalent among autoimmune diseases.
- Reidel's thyroiditis involves IgG4 antibodies, leading to fibrosis and potentially hypothyroidism due to tissue replacement.
Iodine Influence on Hypothyroidism
- Both iodine deficiency and excess can result in hypothyroidism.
- Deficiency hinders functional thyroid hormone synthesis, more common in non-iodine fortified regions.
- Excess iodine can inhibit hormone production via the Wolf-Chaikoff effect.
Central Hypothyroidism Causes
- Arises from hypothalamic or pituitary issues affecting TRH and TSH production.
- Pituitary dysfunction may result from trauma or tumors, including Sheehan syndrome from postpartum hemorrhage.
Congenital Hypothyroidism
- Can occur due to maternal antibodies or developmental issues such as thyroid agenesis.
- Involves dysfunction of thyroid peroxidase, leading to dysgenetic goiter.
- Iodine deficiency is also a major contributor.
Clinical Features of Hypothyroidism
- Goiter may develop from thyroglobulin accumulation due to inadequate hormone release.
- Symptoms include weight gain, cold intolerance, bradycardia, hypertension, and neurological effects like depression and fatigue.
- Compromised bone growth may lead to short stature.
Seven 'P' Mnemonic for Congenital Hypothyroidism Symptoms
- Pot belly
- Pale skin
- Puffy face
- Protruding tongue
- Protruding umbilicus
- Poor brain development
- Prolonged neonatal jaundice
Deep Tendon Reflexes and Myopathy
- Hypothyroidism leads to delayed reflexes (Wolffian sign).
- Muscle contraction and growth hindered, possibly resulting in myopathy with elevated creatinine kinase.
Gastrointestinal Effects
- Hypothyroidism decreases GI motility, causing constipation and potential complications like hemorrhoids due to hard stools.
Skin, Hair, and Nails Changes
- Reduced blood flow leads to hair loss (Queen's sign) and brittle nails.
- Skin appears dry and pale due to decreased secretions and inadequate sebum production.
Liver Function and Lipid Metabolism
- Thyroid hormones regulate LDL and triglyceride receptor activity.
- Low thyroid hormone levels increase LDL and triglycerides, resulting in hypercholesterolemia and hypertriglyceridemia.
Reproductive System Effects
- Hyperprolactinemia from hypothyroidism interferes with sex hormone production.
- Male symptoms: decreased sperm production, low libido, gynecomastia, erectile dysfunction.
- Female symptoms: decreased estrogen, menstrual issues, and possible infertility; increased prolactin can cause galactorrhea.
Edema and Connective Tissue Changes
- Low thyroid hormone increases glycosaminoglycans (GAGs), leading to tissue edema.
- Pre-tibial and periorbital edema can occur from GAG accumulation, potentially causing carpal tunnel syndrome.
Diagnostic Approach to Hypothyroidism
- Differentiating primary from central causes via thyroid function tests for free T4 and TSH levels.
- Low free T4 and high TSH indicate primary hypothyroidism; low free T4 with low TSH indicates central issues.
- MRI helps identify hypothalamic or pituitary lesions.
Primary Causes of Hypothyroidism
- Hashimoto's thyroiditis: confirmed by positive TPO and thyroglobulin antibodies; biopsy may be needed.
- Postpartum thyroiditis manifests within a year of childbirth, typically acute.
- Drug-induced hypothyroidism requires careful patient history and identification of relevant medications.
- Diagnosing renal thyroiditis necessitates evaluating fibrous tissue indicators.
Thyroid Hormone Physiology
- Hypothalamus secretes thyrotropin releasing hormone (TRH).
- TRH stimulates anterior pituitary to release thyroid stimulating hormone (TSH).
- TSH prompts thyroid gland to produce thyroxine (T4, 90%) and triiodothyronine (T3, 10%).
- T4 is converted to active T3 within cells by D-iodinases.
- T3 enhances metabolism and gene expression by binding to intracellular receptors.
Metabolic Effects of Thyroid Hormone
- Increases overall metabolism through:
- Glycogenolysis: breaking down glycogen to glucose.
- Glycolysis: converting glucose to pyruvate.
- Lipolysis: converting lipids into fatty acids and glycerol.
- Stimulates sodium-potassium ATPase, increasing ATP usage and energy production.
Impact on Various Systems
-
Cardiovascular:
- Enhances beta-adrenergic receptor sensitivity, increasing heart rate and contractility.
- Balances vasomotor tone between vasoconstriction and vasodilation.
-
Skeletal:
- Regulates osteoclasts and osteoblasts, affecting bone remodeling and calcium metabolism.
-
Nervous:
- Activates the sympathetic nervous system.
-
Gastrointestinal:
- Improves GI motility and secretion.
-
Skin and Hair:
- Increases blood flow to skin, promoting growth of hair and nails.
- Regulates function of sebaceous and sweat glands.
-
Reproductive:
- Assists in the regulation of sex hormone binding globulin and LH/FSH levels.
-
Muscular:
- Supports muscle development and contraction through calcium ATPase regulation.
Primary Hypothyroidism
- Common causes include thyroid antibodies, viral infections, and drug damage.
-
Hashimoto's Thyroiditis:
- Autoimmune condition mainly affecting females; antibodies target thyroid peroxidase and thyroglobulin.
- Associated with HLA-DR3 and HLA-DR5 allele susceptibility.
-
Postpartum Thyroiditis:
- Occurs within a year after childbirth, often resolves naturally.
-
Subacute Granulomatous Thyroiditis:
- Caused by viral infections leading to inflammation and elevated ESR.
-
Drug-Induced Hypothyroidism:
- Results from medications like amiodarone, lithium, and iodine-131 affecting hormone synthesis.
Pathophysiology and Symptoms
- Initial thyroid gland damage may cause transient hyperthyroidism.
- Prolonged damage results in hypothyroidism symptoms like fatigue, weight gain, and cold intolerance.
Hashimoto's vs. Reidel's Thyroiditis
- Hashimoto's is prevalent among autoimmune diseases.
- Reidel's thyroiditis involves IgG4 antibodies, leading to fibrosis and potentially hypothyroidism due to tissue replacement.
Iodine Influence on Hypothyroidism
- Both iodine deficiency and excess can result in hypothyroidism.
- Deficiency hinders functional thyroid hormone synthesis, more common in non-iodine fortified regions.
- Excess iodine can inhibit hormone production via the Wolf-Chaikoff effect.
Central Hypothyroidism Causes
- Arises from hypothalamic or pituitary issues affecting TRH and TSH production.
- Pituitary dysfunction may result from trauma or tumors, including Sheehan syndrome from postpartum hemorrhage.
Congenital Hypothyroidism
- Can occur due to maternal antibodies or developmental issues such as thyroid agenesis.
- Involves dysfunction of thyroid peroxidase, leading to dysgenetic goiter.
- Iodine deficiency is also a major contributor.
Clinical Features of Hypothyroidism
- Goiter may develop from thyroglobulin accumulation due to inadequate hormone release.
- Symptoms include weight gain, cold intolerance, bradycardia, hypertension, and neurological effects like depression and fatigue.
- Compromised bone growth may lead to short stature.
Seven 'P' Mnemonic for Congenital Hypothyroidism Symptoms
- Pot belly
- Pale skin
- Puffy face
- Protruding tongue
- Protruding umbilicus
- Poor brain development
- Prolonged neonatal jaundice
Deep Tendon Reflexes and Myopathy
- Hypothyroidism leads to delayed reflexes (Wolffian sign).
- Muscle contraction and growth hindered, possibly resulting in myopathy with elevated creatinine kinase.
Gastrointestinal Effects
- Hypothyroidism decreases GI motility, causing constipation and potential complications like hemorrhoids due to hard stools.
Skin, Hair, and Nails Changes
- Reduced blood flow leads to hair loss (Queen's sign) and brittle nails.
- Skin appears dry and pale due to decreased secretions and inadequate sebum production.
Liver Function and Lipid Metabolism
- Thyroid hormones regulate LDL and triglyceride receptor activity.
- Low thyroid hormone levels increase LDL and triglycerides, resulting in hypercholesterolemia and hypertriglyceridemia.
Reproductive System Effects
- Hyperprolactinemia from hypothyroidism interferes with sex hormone production.
- Male symptoms: decreased sperm production, low libido, gynecomastia, erectile dysfunction.
- Female symptoms: decreased estrogen, menstrual issues, and possible infertility; increased prolactin can cause galactorrhea.
Edema and Connective Tissue Changes
- Low thyroid hormone increases glycosaminoglycans (GAGs), leading to tissue edema.
- Pre-tibial and periorbital edema can occur from GAG accumulation, potentially causing carpal tunnel syndrome.
Diagnostic Approach to Hypothyroidism
- Differentiating primary from central causes via thyroid function tests for free T4 and TSH levels.
- Low free T4 and high TSH indicate primary hypothyroidism; low free T4 with low TSH indicates central issues.
- MRI helps identify hypothalamic or pituitary lesions.
Primary Causes of Hypothyroidism
- Hashimoto's thyroiditis: confirmed by positive TPO and thyroglobulin antibodies; biopsy may be needed.
- Postpartum thyroiditis manifests within a year of childbirth, typically acute.
- Drug-induced hypothyroidism requires careful patient history and identification of relevant medications.
- Diagnosing renal thyroiditis necessitates evaluating fibrous tissue indicators.
Thyroid Hormone Physiology
- Hypothalamus secretes thyrotropin releasing hormone (TRH).
- TRH stimulates anterior pituitary to release thyroid stimulating hormone (TSH).
- TSH prompts thyroid gland to produce thyroxine (T4, 90%) and triiodothyronine (T3, 10%).
- T4 is converted to active T3 within cells by D-iodinases.
- T3 enhances metabolism and gene expression by binding to intracellular receptors.
Metabolic Effects of Thyroid Hormone
- Increases overall metabolism through:
- Glycogenolysis: breaking down glycogen to glucose.
- Glycolysis: converting glucose to pyruvate.
- Lipolysis: converting lipids into fatty acids and glycerol.
- Stimulates sodium-potassium ATPase, increasing ATP usage and energy production.
Impact on Various Systems
-
Cardiovascular:
- Enhances beta-adrenergic receptor sensitivity, increasing heart rate and contractility.
- Balances vasomotor tone between vasoconstriction and vasodilation.
-
Skeletal:
- Regulates osteoclasts and osteoblasts, affecting bone remodeling and calcium metabolism.
-
Nervous:
- Activates the sympathetic nervous system.
-
Gastrointestinal:
- Improves GI motility and secretion.
-
Skin and Hair:
- Increases blood flow to skin, promoting growth of hair and nails.
- Regulates function of sebaceous and sweat glands.
-
Reproductive:
- Assists in the regulation of sex hormone binding globulin and LH/FSH levels.
-
Muscular:
- Supports muscle development and contraction through calcium ATPase regulation.
Primary Hypothyroidism
- Common causes include thyroid antibodies, viral infections, and drug damage.
-
Hashimoto's Thyroiditis:
- Autoimmune condition mainly affecting females; antibodies target thyroid peroxidase and thyroglobulin.
- Associated with HLA-DR3 and HLA-DR5 allele susceptibility.
-
Postpartum Thyroiditis:
- Occurs within a year after childbirth, often resolves naturally.
-
Subacute Granulomatous Thyroiditis:
- Caused by viral infections leading to inflammation and elevated ESR.
-
Drug-Induced Hypothyroidism:
- Results from medications like amiodarone, lithium, and iodine-131 affecting hormone synthesis.
Pathophysiology and Symptoms
- Initial thyroid gland damage may cause transient hyperthyroidism.
- Prolonged damage results in hypothyroidism symptoms like fatigue, weight gain, and cold intolerance.
Hashimoto's vs. Reidel's Thyroiditis
- Hashimoto's is prevalent among autoimmune diseases.
- Reidel's thyroiditis involves IgG4 antibodies, leading to fibrosis and potentially hypothyroidism due to tissue replacement.
Iodine Influence on Hypothyroidism
- Both iodine deficiency and excess can result in hypothyroidism.
- Deficiency hinders functional thyroid hormone synthesis, more common in non-iodine fortified regions.
- Excess iodine can inhibit hormone production via the Wolf-Chaikoff effect.
Central Hypothyroidism Causes
- Arises from hypothalamic or pituitary issues affecting TRH and TSH production.
- Pituitary dysfunction may result from trauma or tumors, including Sheehan syndrome from postpartum hemorrhage.
Congenital Hypothyroidism
- Can occur due to maternal antibodies or developmental issues such as thyroid agenesis.
- Involves dysfunction of thyroid peroxidase, leading to dysgenetic goiter.
- Iodine deficiency is also a major contributor.
Clinical Features of Hypothyroidism
- Goiter may develop from thyroglobulin accumulation due to inadequate hormone release.
- Symptoms include weight gain, cold intolerance, bradycardia, hypertension, and neurological effects like depression and fatigue.
- Compromised bone growth may lead to short stature.
Seven 'P' Mnemonic for Congenital Hypothyroidism Symptoms
- Pot belly
- Pale skin
- Puffy face
- Protruding tongue
- Protruding umbilicus
- Poor brain development
- Prolonged neonatal jaundice
Deep Tendon Reflexes and Myopathy
- Hypothyroidism leads to delayed reflexes (Wolffian sign).
- Muscle contraction and growth hindered, possibly resulting in myopathy with elevated creatinine kinase.
Gastrointestinal Effects
- Hypothyroidism decreases GI motility, causing constipation and potential complications like hemorrhoids due to hard stools.
Skin, Hair, and Nails Changes
- Reduced blood flow leads to hair loss (Queen's sign) and brittle nails.
- Skin appears dry and pale due to decreased secretions and inadequate sebum production.
Liver Function and Lipid Metabolism
- Thyroid hormones regulate LDL and triglyceride receptor activity.
- Low thyroid hormone levels increase LDL and triglycerides, resulting in hypercholesterolemia and hypertriglyceridemia.
Reproductive System Effects
- Hyperprolactinemia from hypothyroidism interferes with sex hormone production.
- Male symptoms: decreased sperm production, low libido, gynecomastia, erectile dysfunction.
- Female symptoms: decreased estrogen, menstrual issues, and possible infertility; increased prolactin can cause galactorrhea.
Edema and Connective Tissue Changes
- Low thyroid hormone increases glycosaminoglycans (GAGs), leading to tissue edema.
- Pre-tibial and periorbital edema can occur from GAG accumulation, potentially causing carpal tunnel syndrome.
Diagnostic Approach to Hypothyroidism
- Differentiating primary from central causes via thyroid function tests for free T4 and TSH levels.
- Low free T4 and high TSH indicate primary hypothyroidism; low free T4 with low TSH indicates central issues.
- MRI helps identify hypothalamic or pituitary lesions.
Primary Causes of Hypothyroidism
- Hashimoto's thyroiditis: confirmed by positive TPO and thyroglobulin antibodies; biopsy may be needed.
- Postpartum thyroiditis manifests within a year of childbirth, typically acute.
- Drug-induced hypothyroidism requires careful patient history and identification of relevant medications.
- Diagnosing renal thyroiditis necessitates evaluating fibrous tissue indicators.
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Description
This quiz covers the physiology of thyroid hormones, focusing on the role of TRH and TSH in stimulating thyroid hormone production. It examines the metabolic effects of thyroid hormones, including their impact on various systems, particularly the cardiovascular system. Test your knowledge on how these hormones enhance metabolic functions and gene expression.
