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Questions and Answers
What is a consequence of calcium deposition in renal tubules?
What is a consequence of calcium deposition in renal tubules?
What condition is characterized by impaired mentation and emotional instability?
What condition is characterized by impaired mentation and emotional instability?
What laboratory finding is typical for diagnosing hypoparathyroidism?
What laboratory finding is typical for diagnosing hypoparathyroidism?
What is a symptom of hypocalcemia that can occur due to hypoparathyroidism?
What is a symptom of hypocalcemia that can occur due to hypoparathyroidism?
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Which of the following is NOT a potential consequence of nephrocalcinosis?
Which of the following is NOT a potential consequence of nephrocalcinosis?
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Which diagnostic test is helpful in assessing bone density?
Which diagnostic test is helpful in assessing bone density?
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What treatment is often required for an individual with hypercalcemia?
What treatment is often required for an individual with hypercalcemia?
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Which of the following symptoms is associated with adrenal malignancy due to ectopic source (ACTH)?
Which of the following symptoms is associated with adrenal malignancy due to ectopic source (ACTH)?
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What is a common consequence of hypercalcemia in the kidneys?
What is a common consequence of hypercalcemia in the kidneys?
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What is a common sign of Cushing's syndrome related to adrenal dysfunction?
What is a common sign of Cushing's syndrome related to adrenal dysfunction?
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What is a likely cause of primary adrenal insufficiency?
What is a likely cause of primary adrenal insufficiency?
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What sign is commonly associated with primary adrenal failure?
What sign is commonly associated with primary adrenal failure?
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Which symptom is NOT commonly associated with hyperparathyroidism?
Which symptom is NOT commonly associated with hyperparathyroidism?
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What is the primary stimulus for the secretion of parathormone (PTH)?
What is the primary stimulus for the secretion of parathormone (PTH)?
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What could be a symptom of adrenal insufficiency?
What could be a symptom of adrenal insufficiency?
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Which of the following is NOT a sign of adrenal malignancy with ectopic ACTH secretion?
Which of the following is NOT a sign of adrenal malignancy with ectopic ACTH secretion?
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What hormone regulates the production, secretion, and growth of thyroid hormones?
What hormone regulates the production, secretion, and growth of thyroid hormones?
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Which of the following describes thyrotoxicosis?
Which of the following describes thyrotoxicosis?
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What is Von Graefe's sign?
What is Von Graefe's sign?
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Which symptom is typically associated with hypothyroidism?
Which symptom is typically associated with hypothyroidism?
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What is one major cause of hyperthyroidism?
What is one major cause of hyperthyroidism?
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Which of the following is NOT a typical symptom of hyperthyroidism?
Which of the following is NOT a typical symptom of hyperthyroidism?
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What laboratory measurement is used to evaluate thyroid function?
What laboratory measurement is used to evaluate thyroid function?
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Which factor is involved in the negative feedback regulation of TSH?
Which factor is involved in the negative feedback regulation of TSH?
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What is the preferred isotope for radio-active iodine uptake testing?
What is the preferred isotope for radio-active iodine uptake testing?
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What is a common physical characteristic seen in a patient with acromegaly?
What is a common physical characteristic seen in a patient with acromegaly?
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Which of the following hormones is primarily involved in raising blood glucose levels?
Which of the following hormones is primarily involved in raising blood glucose levels?
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What is one of the most common causes of Cushing syndrome?
What is one of the most common causes of Cushing syndrome?
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What effect does excessive growth hormone have on the skin?
What effect does excessive growth hormone have on the skin?
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Which of the following is NOT a symptom associated with acromegaly?
Which of the following is NOT a symptom associated with acromegaly?
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Which of the following statements about the adrenal gland is correct?
Which of the following statements about the adrenal gland is correct?
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What is a consequence of growth hormone excess in terms of bone structure?
What is a consequence of growth hormone excess in terms of bone structure?
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What is the primary functional role of the thyroid gland?
What is the primary functional role of the thyroid gland?
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Which of the following hormones is primarily secreted by the thyroid gland?
Which of the following hormones is primarily secreted by the thyroid gland?
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How is the majority of circulating T3 produced?
How is the majority of circulating T3 produced?
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What percentage of circulating T4 is typically unbound and metabolically active?
What percentage of circulating T4 is typically unbound and metabolically active?
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Which plasma carrier protein binds the largest proportion of circulating T4?
Which plasma carrier protein binds the largest proportion of circulating T4?
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What is one of the effects of thyroid hormone on the heart?
What is one of the effects of thyroid hormone on the heart?
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Which of the following is a critical role of T3 in bone development?
Which of the following is a critical role of T3 in bone development?
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What is the recommended minimum daily iodine intake?
What is the recommended minimum daily iodine intake?
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Which one of these effects is caused by thyroid hormones on metabolism?
Which one of these effects is caused by thyroid hormones on metabolism?
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What controls the function of the thyroid gland?
What controls the function of the thyroid gland?
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Study Notes
Thyroid Gland and Thyroid Hormones
- The thyroid gland is responsible for secreting thyroid hormones and calcitonin, a hormone essential for calcium homeostasis.
- The thyroid gland is made up of follicles, which are the functional units of the gland.
- The thyroid gland produces two metabolic hormones: thyroxine (T4) and triiodothyronine (T3).
- T4 is the primary secretory product of the thyroid gland, while T3 is derived from both direct thyroid secretion and deiodination of T4 in peripheral tissues.
- Iodine is essential for thyroid hormone production and can be obtained from various sources, including seafood, bread, dairy products, and iodized salt.
- Most circulating thyroid hormones are bound to plasma carrier proteins, including thyroxine-binding globulin (TBG), transthyretin (TTR), and albumin.
- Only unbound (free) thyroid hormone has metabolic activity and physiologic effects.
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Effects of thyroid hormone:
- Fetal brain and skeletal maturation
- Increase in basal metabolic rate
- Inotropic and chronotropic effects on the heart
- Increases sensitivity to catecholamines
- Stimulates gut motility
- Increases bone turnover
- Leads to increased serum glucose and decreased serum cholesterol levels.
- Thyroid hormone is crucial for normal bone growth and development, regulating the expression of factors involved in linear growth at the growth plate.
- The hypothalamus-pituitary-thyroid (HPT) axis regulates thyroid hormone production and secretion.
- The hypothalamus releases thyrotropin-releasing hormone (TRH).
- TRH stimulates the anterior pituitary to release thyroid-stimulating hormone (TSH).
- TSH further promotes thyroid hormone secretion.
Hyperthyroidism and Thyrotoxicosis
- Thyrotoxicosis refers to the clinical syndrome resulting from exposure to high levels of circulating thyroid hormones.
- Most cases of thyrotoxicosis are caused by hyperthyroidism, which is hyperactivity of the thyroid gland.
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Clinical manifestations of hyperthyroidism:
- Goiter
- Weight loss
- Rapid heart rate
- Increased appetite
- Heat intolerance
- Tremor
- Nervousness
- Weakness
- Diarrhea
- Insomnia
- Exophthalmos (bulging eyes)
- Von Graefe's sign (upper eyelid lags behind the eyeball when looking downwards)
- Joffroy's sign (absence of forehead wrinkling when looking upwards with the face inclined downwards)
- Hair loss
- Brittle nails
- Irregular menses
- Increased sweating
- Fatigue and muscle weakness
- Emotional lability
Hypothyroidism
- Hypothyroidism occurs when the thyroid gland produces insufficient thyroid hormones.
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Clinical manifestations of hypothyroidism:
- Dry hair
- Puffy face
- Slow heart rate
- Weight gain
- Constipation
- Cold intolerance
- Depression
- Dry skin
- Fatigue
- Memory loss
- Heavy menstrual periods
- Muscle aches
- Decreased fertility
Evaluation of Thyroid Function
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Laboratory investigations for thyroid function:
- Total T4 (normal: 4-12 ug/dl)
- Total T3 (normal: 80-120 ng/dl)
- Free T3 and T4
- Radioactive Iodine Uptake (RAIU)
- Serum TSH
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Other investigations:
- Thyroid ultrasound
- Fine needle aspiration biopsy
Pituitary Gland and Growth Hormone
- The pituitary gland produces growth hormone (GH), which regulates growth, metabolism, and protein synthesis.
- Growth hormone increases blood glucose, protein synthesis, and free fatty acid levels.
Acromegaly
- Acromegaly is a condition caused by excessive GH secretion, typically due to a pituitary adenoma (benign tumor).
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Clinical manifestations of acromegaly:
- Coarse facial features
- Enlarged soft tissue in the nose, lips and tongue
- Overgrowth of the jawbone (prognathism)
- Enlarged hands and feet
- Coarse body hair
- Excessive sweating
- Deep and husky voice
- Joint pain
- Cardiomegaly, hypertension, and hepatomegaly
- Compression of nerves leading to sensory disturbances and weakness in the arms and legs
- Headaches
- Irregular menstrual cycles
Adrenal Gland Disorders
- The adrenal glands produce cortisol, mineralocorticoids, and androgens (from the cortex) and adrenaline (epinephrine) from the medulla.
Cushing syndrome
- Cushing syndrome occurs due to excess cortisol circulating in the blood stream.
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Etiologies of Cushing syndrome:
- Iatrogenic (steroid therapy)
- Pituitary adenoma (ACTH-producing)
- Adrenal adenoma
- Adrenal hyperplasia
- Adrenal malignancy
- Ectopic ACTH production (e.g., small cell carcinoma of the lung)
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Clinical manifestations of Cushing syndrome:
- Mood changes (depression and euphoria)
- Easy bruising
- Weakness
- Weight gain
- Amenorrhea
- Back pain
- Moon face
- Truncal obesity
- Buffalo hump
- Purple and pink stretch marks (striae rubra)
- High blood pressure
- Osteoporosis
- Thinning skin, prone to bruising and slow healing
- Diabetes
- Increased risk of infections
- Hirsutism (abnormal hair growth)
- Hair loss
Adrenal Hypofunction
- Adrenal hypofunction refers to insufficient adrenal gland hormone secretion.
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Etiologies of adrenal hypofunction:
- Secondary (pituitary insufficiency)
- Primary (Addison's disease):
- Primary adrenal failure caused by destruction of the adrenal glands, often due to:
- Granulomatous disease (e.g., tuberculosis, fungus)
- Amyloidosis
- Hemochromatosis
- Tumor
- Autoimmune processes
- Primary adrenal failure caused by destruction of the adrenal glands, often due to:
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Clinical manifestations of adrenal hypofunction:
- Weakness, tiredness, dizziness
- Fatigue and lethargy
- Nausea, vomiting, and weight loss
- Diarrhea and dehydration
- Salt craving
- Abdominal pain
- Hyperpigmentation (skin darkening)
- Pigmented buccal mucosa
- Hypotension
- Reduced hair growth
- Signs of dehydration
Parathyroid Gland
- The parathyroid glands are four small glands located in the neck, responsible for secreting parathyroid hormone (PTH).
- PTH plays a crucial role in maintaining calcium homeostasis in the blood.
- The primary stimulus for PTH secretion is hypocalcemia (low blood calcium levels).
Hyperparathyroidism
- Hyperparathyroidism occurs when the parathyroid glands produce excessive PTH.
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Clinical manifestations of hyperparathyroidism:
- Most patients are asymptomatic.
- Non-specific symptoms such as weakness and fatigue
- Hypercalcemia-related symptoms:
- Anorexia, nausea, and vomiting
- Dyspepsia
- Constipation
- Increased risk of peptic ulcer and acute pancreatitis
- Interstitial nephritis (deposition of calcium in the renal tubules leading to inability to concentrate urine)
- Polyuria, polydipsia, and nocturia
- Increased susceptibility to renal stones (calcium oxalate and phosphate stones)
- Nephrocalcinosis (whole kidney calcification)
- Impaired mentation, memory loss, emotional lability, depression, anosmia, drowsiness, stupor, and coma
- Weakness in proximal muscles
- Arthralgia (joint pain)
- Severe pruritus (calcification of the skin)
- Calcification at the corneoscleral junction (keratitis and corneal opacity)
- Solitary bone resorption
- Osteitis fibrosa cystica
Diagnosis of Hyperparathyroidism
-
Laboratory investigations:
- Hypercalcemia (normal: 9-11 mg/100 ml)
- Hypophosphatemia (normal: 2.5-4 mg/100 ml)
- Increased alkaline phosphatase
- Increased PTH level
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Other investigations:
- Urinalyses and kidney X-rays
- Bone density test
Treatment of Hyperparathyroidism
- Medical management of hypercalcemia
- Surgical removal of the affected parathyroid gland
Hypoparathyroidism
- Hypoparathyroidism occurs due to insufficient PTH secretion, often caused by surgical procedures or autoimmune disorders.
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Clinical manifestations of hypoparathyroidism:
- Asymptomatic or manifestations of hypocalcemia:
- Neuromuscular activity disturbances (numbness, tingling, paresthesia)
- Bronchospasm or laryngeal spasm (stridor)
- Carpopedal spasm (spasmodic contractions in the hands and feet)
- Asymptomatic or manifestations of hypocalcemia:
Diagnosis of Hypoparathyroidism
-
Laboratory investigations:
- Decreased serum calcium
- Increased phosphate in the absence of renal failure
- Low PTH levels
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Description
Explore the essential functions of the thyroid gland and its hormones, including thyroxine (T4) and triiodothyronine (T3). Learn about the significance of iodine in hormone production and the role of thyroid hormones in metabolism and development. This quiz covers the structure, function, and impact of thyroid hormones on the body.
