Thyroid Hormones and Pituitary Function Quiz
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Questions and Answers

Which of the following statements accurately describes the role of thyroglobulin in thyroid hormone synthesis?

  • Thyroglobulin directly activates the synthesis of T3 and T4 by binding to and activating the enzymes responsible for their synthesis.
  • Thyroglobulin acts as a carrier protein for iodine in the bloodstream, transporting it to the thyroid gland.
  • Thyroglobulin is a precursor protein to thyroxine (T4) and triiodothyronine (T3), and it is iodinated to form these hormones. (correct)
  • Thyroglobulin regulates the release of T3 and T4 from the thyroid gland, preventing their premature release into the bloodstream.

    • Which of the following statements correctly describes the relationship between TSH and calcitonin?

  • TSH and calcitonin have opposing effects on blood calcium levels, with TSH increasing levels and calcitonin decreasing them.
  • TSH stimulates thyroid hormone synthesis and release, while calcitonin inhibits bone resorption, leading to a decrease in blood calcium levels. (correct)
  • TSH and calcitonin are both secreted by the thyroid gland and have synergistic effects, both lowering blood calcium levels.
  • TSH stimulates calcitonin secretion from the parafollicular cells of the thyroid gland.

    • Which of the following statements best explains the lag period observed in thyroid hormone action?

  • Thyroid hormones act primarily by regulating gene expression, which takes time for the synthesis of new proteins. (correct)
  • The lag period is due to the time required for T3 and T4 to be transported from the thyroid gland to target tissues.
  • The lag period is a result of the slow rate of diffusion of thyroid hormones through the cell membrane and into the cytoplasm.
  • The lag period is caused by the slow rate of conversion of T4 to the biologically active form, T3.

    • Which of the following statements accurately describes the differences between T3 and T4?

    <p>T3 has a shorter half-life than T4 and is more rapidly metabolized in the body. (D)</p> Signup and view all the answers

    Which of the following is NOT a step involved in the synthesis of thyroid hormone?

    <p>Direct binding of T3 and T4 to thyroglobulin molecules within the colloid. (D)</p> Signup and view all the answers

    In a short feedback loop within the Hypothalamo-Pituitary-Target axis, which of the following scenarios is always correct?

    <p>The pituitary's hormone directly inhibits the hypothalamus. (A)</p> Signup and view all the answers

    What is the role of the Thalamus in relation to the Hypothalamus?

    <p>The Thalamus provides information about pain perception to the Hypothalamus, which then triggers appropriate responses. (C)</p> Signup and view all the answers

    How does the Posterior Pituitary differ from the Anterior Pituitary in terms of hormone production?

    <p>Both Pituitaries produce hormones, but the Posterior Pituitary primarily releases hormones produced by neurons in the Hypothalamus, while the Anterior Pituitary produces its own hormones. (C)</p> Signup and view all the answers

    Which of the following is NOT a characteristic of positive feedback loops in the Hypothalamic-Pituitary-Target axis?

    <p>They are directly involved in maintaining homeostasis around a stable intrinsic/preset level. (B)</p> Signup and view all the answers

    Which of the following is NOT a direct output of the Hypothalamus?

    <p>The Sympathetic Nervous System (C)</p> Signup and view all the answers

    What is the primary role of the Reticular Activating System (RAS) in relation to the Hypothalamus?

    <p>The RAS serves as a regulator of sleep and wakefulness, sending signals to the Hypothalamus to adjust hormone levels. (A)</p> Signup and view all the answers

    Where are the axon terminals of neurons responsible for releasing Oxytocin and ADH located?

    <p>The Posterior Pituitary (C)</p> Signup and view all the answers

    The 'Short Portal Vein' is responsible for what crucial connection?

    <p>Facilitating communication between the Posterior Pituitary and the Anterior Pituitary by transporting hormones. (B)</p> Signup and view all the answers

    What is the primary function of the Hypothalamus in the Hypothalamo-Pituitary-Target Axis?

    <p>To integrate internal and external signals and direct the release of specific hormones from the Pituitary. (B)</p> Signup and view all the answers

    A patient presents with symptoms suggesting hyperthyroidism. A basal thyroid hormone test reveals high levels of thyroid hormones. What is the next logical step in assessing the potential cause of hyperthyroidism?

    <p>Perform a dynamic thyroid hormone test to assess thyroid gland responsiveness. (A)</p> Signup and view all the answers

    A patient presents with symptoms of hypothyroidism. A basal test reveals low levels of thyroid-stimulating hormone (TSH). Which of the following is the MOST likely diagnosis based on this information alone?

    <p>Secondary hypothyroidism (A)</p> Signup and view all the answers

    A patient exhibits symptoms of excess cortisol production. A dynamic test using dexamethasone, a synthetic cortisol analogue, does not suppress cortisol levels. What is the MOST likely explanation for this finding?

    <p>Adrenal gland tumor (C)</p> Signup and view all the answers

    Which of the following is a valid reason for performing a dynamic hormone test, as opposed to a basal hormone test, in evaluating an endocrine disorder?

    <p>Dynamic tests can help identify the source of hormonal dysfunction within the hypothalamo-pituitary axis. (A)</p> Signup and view all the answers

    A patient with suspected hyperprolactinemia undergoes a dynamic test using dopamine, a prolactin inhibitor. The prolactin levels remain elevated despite the dopamine administration. Which of the following is the MOST likely explanation?

    <p>Pituitary adenoma (C)</p> Signup and view all the answers

    In the context of endocrine disorders, what is the difference between 'loss of suppression' and 'hyperstimulation' as potential causes of hormonal imbalances?

    <p>Loss of suppression refers to a failure of negative feedback mechanisms, while hyperstimulation refers to an overactive gland due to excessive stimulation. (A)</p> Signup and view all the answers

    A patient presents with symptoms of Cushing's syndrome. Which of the following dynamic hormone tests would be MOST helpful in determining the cause of Cushing's syndrome?

    <p>Dexamethasone suppression test (C)</p> Signup and view all the answers

    Which hormone acts as a growth factor during the fetal phase of growth?

    <p>Insulin (A)</p> Signup and view all the answers

    Which phase of growth is characterized by a significant peak in growth velocity followed by a plateau?

    <p>Post-pubertal (Late Teens) (B)</p> Signup and view all the answers

    Which hormone exerts a permissive role in growth, meaning it enhances the effectiveness of other growth hormones?

    <p>Cortisol (B)</p> Signup and view all the answers

    How do sex hormones influence growth during puberty?

    <p>They promote the fusion of epiphyseal plates, limiting further bone elongation. (A)</p> Signup and view all the answers

    Which of the following is NOT a major hormone involved in growth regulation?

    <p>Adrenocorticotropic hormone (ACTH) (B)</p> Signup and view all the answers

    What is the primary site of production for Growth-Hormone Releasing Factor (GRF) in the body?

    <p>Hypothalamus (C)</p> Signup and view all the answers

    Which of the following factors directly influences the effectiveness of growth hormone during the infantile phase?

    <p>The presence of sufficient IGF-I levels. (A)</p> Signup and view all the answers

    Which of the following statements accurately describes the role of genetics in growth regulation?

    <p>Genetic factors determine the overall growth potential, but environmental factors can significantly modify this potential. (D)</p> Signup and view all the answers

    Which of the following is NOT a direct action of Somatostatin on the release of hormones from the anterior pituitary?

    <p>Growth Hormone (GH) (B)</p> Signup and view all the answers

    Which of the following correctly describes the relationship between Growth Hormone (GH) and Insulin-like Growth Factor (IGF)?

    <p>GH stimulates the synthesis of IGF, which then acts as a mediator of many of GH's effects. (B)</p> Signup and view all the answers

    What is the most likely cause of a secondary pituitary deficiency leading to growth hormone deficiency?

    <p>A tumor in the pituitary gland that compresses the pituitary stalk, preventing the release of GRH from the hypothalamus. (A)</p> Signup and view all the answers

    Which of the following is a direct metabolic effect of Growth Hormone (GH)?

    <p>Stimulation of protein synthesis in the liver. (C)</p> Signup and view all the answers

    What is the primary difference between Gigantism and Acromegaly?

    <p>Gigantism affects children, while Acromegaly affects adults. (C)</p> Signup and view all the answers

    Which of the following scenarios would be classified as a primary growth hormone deficiency?

    <p>A child with a defect in the hypothalamus preventing the release of GRH. (D)</p> Signup and view all the answers

    Which of the following is NOT a recognized cause of hypersecretion of growth hormone?

    <p>Precocious puberty, due to increased production of sex hormones. (D)</p> Signup and view all the answers

    Which of the following statements regarding the regulation of growth hormone (GH) release is TRUE?

    <p>Somatostatin inhibits the release of GRH. (C)</p> Signup and view all the answers

    In addition to its effects on growth and metabolism, what other function is attributed to Growth Hormone (GH)?

    <p>Enhancement of immune function. (C)</p> Signup and view all the answers

    Which of the following is a possible consequence of hyposecretion of Growth Hormone (GH) occurring in childhood?

    <p>Short stature. (B)</p> Signup and view all the answers

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    Flashcards

    Hyper-secretion

    Excessive production of hormones by a gland.

    Loss of suppression

    Failure to reduce hormone levels when needed, leading to excess.

    Ectopic sites of secretion

    Hormones released from tumors located away from target glands.

    Primary endocrine disorder

    A disorder originating in the target gland itself.

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    Secondary endocrine disorder

    A disorder originating in the pituitary gland affecting target glands.

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    Tertiary endocrine disorder

    A disorder originating in the hypothalamus affecting the pituitary gland.

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    Dynamic hormone testing

    Testing the responsiveness of glands by stimulating or suppressing hormone activity.

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    Posterior Pituitary

    A gland that releases hormones like Oxytocin and ADH from neuron terminals via exocytosis.

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    Oxytocin

    A hormone synthesized in the hypothalamus, involved in childbirth and bonding.

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    ADH

    Antidiuretic hormone that helps regulate water balance in the body.

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    Hypothalamus

    A brain region that integrates signals and controls hormone release from the pituitary.

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    Negative Feedback Control

    A mechanism where the response decreases hormone release to maintain balance.

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    Positive Feedback Control

    An uncommon mechanism where the response increases hormone release, often in specific scenarios.

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    Ultra-Short Loop

    Feedback where the secreted hormone acts back on the same tissue that produced it.

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    Short Loop Feedback

    Feedback where the hormone from the target organ influences the pituitary or hypothalamus.

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    Long Loop Feedback

    Feedback where the hormone from the target organ directly influences the hypothalamus.

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    T4 Thyroxine

    A thyroid hormone with 4 iodines, less active than T3.

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    T3 Triiodothyronine

    The most biologically active thyroid hormone with 3 iodines, 7% of total.

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    Calcitonin

    Hormone secreted by parafollicular cells to lower plasma calcium.

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    Thyroid hormone synthesis steps

    Process includes iodide uptake, activation, and T3/T4 synthesis.

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    Thyroid hormone release mechanism

    Colloid endocytosed and cleaved to release T3 & T4 into blood.

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    Phases of Growth

    Stages of growth (Foetal, Infantile, Pre-Pubertal, Pubertal, Post-Pubertal) differing in rates and regulators.

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    Foetal Growth Phase

    In utero phase where nutrition and insulin are crucial for growth.

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    Infantile Growth Phase

    Phase from birth to 2 years where growth depends on nutrition and low levels of GH & IGF.

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    Pre-Pubertal Phase

    Childhood phase with declining growth velocity, influenced by malnutrition and increased IGF levels.

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    Pubertal Growth Phase

    Early teens phase with peak growth influenced by sex hormones and GH.

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    Growth Hormone (GH)

    A hormone promoting growth, released by the anterior pituitary gland.

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    Insulin-like Growth Factors (IGF)

    Hormones (IGF-I & IGF-II) that mediate growth effects of GH.

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    Somatostatin

    Hormone that inhibits GH release from the anterior pituitary.

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    Thyroid Hormone

    Hormone that supports growth and metabolic processes.

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    Growth Hormone Releasing Factor (GRF)

    Hormone produced mainly in the hypothalamus that stimulates GH release.

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    Growth Hormone

    A hormone produced by the anterior pituitary that promotes growth and metabolic processes.

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    Regulation of Growth Hormone Release

    Stimulation via GRH and inhibition via somatostatin.

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    IGF

    Insulin-like Growth Factor; promotes growth and development linked to growth hormone.

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    Metabolic Effects of Growth Hormone

    Stimulates lipolysis, ketogenesis, gluconeogenesis, and protein synthesis.

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    Hypersecretion of Growth Hormone

    Excess growth hormone leading to conditions like gigantism and acromegaly.

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    Hyposecretion of Growth Hormone

    Deficiency in growth hormone, leading to stunted growth.

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    Precocious Puberty

    Early onset of puberty not necessarily related to growth hormone.

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    Somatotropes

    Cells in the anterior pituitary that produce growth hormone.

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    Types of GH Deficiency

    Can be primary (hypothalamus/pituitary defect) or secondary (tumors/disease).

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    Study Notes

    Endocrine System File List

    • Overview of the Endocrine System
    • The Hypothalamo-Pituitary Axis
    • Thyroid Function
    • Insulin, Glucagon & Metabolism Regulation
    • Fluid & Electrolyte Balance
    • Calcium & Phosphate Metabolism
    • Physiological Response to Stress
    • Reproductive Endocrinology
    • ADH Disorders
    • Adrenal Cortex Dysfunction
    • Adrenal Medulla Dysfunction
    • Calcium & Phosphate Imbalance Disorders
    • Diabetes
    • Diabetic Emergencies
    • Gonadal Dysfunction
    • Growth Dysfunction
    • MENs Multiple Endocrine Neoplasia Syndrome
    • Pituitary Dysfunction
    • Thyroid Dysfunction
    • Free bonus: Endocrinology chapter of Toronto Notes for reference and further detailed reading.

    Hormone Families

    • Amino Acid Derivatives
    • Catecholamines (adrenaline, noradrenaline, dopamine) derived from tyrosine
    • Histamine derived from histidine
    • Thyroid hormones derived from tyrosine
    • Proteins
    • Pituitary hormones
    • Steroids
    • Sex hormones derived from cholesterol
    • Fatty Acid Derivatives
    • Prostaglandins
    • Thromboxanes, etc.
    • Purines
    • Gases
    • Nitric Oxide
    • Acetylcholine

    Hormone Synthesis

    • Steroidogenesis
    • All steroid hormones are derived from cholesterol.
    • 5 families, each with a key physiological member:
    • Progestagens (progesterone)
    • Androgens (testosterone)
    • Mineralocorticoids (aldosterone)
    • Glucocorticoids (cortisol)
    • Estrogens (estrogen)
    • Protein/Peptide Synthesis & Processing
    • Some protein hormones are initially synthesised as longer pre-prohormones.
    • Pre-prohormones cleave to prohormones, and those to active hormones.

    Properties of Chemical Messengers

    • Biological Specificity: hormones only bind to specific receptors.
    • Affinity: the degree of attraction between hormone and receptor.
    • Efficacy: The degree of effectiveness of the binding.
    • Agonists: have high affinity and efficacy.
    • Antagonists: have high affinity but low efficacy.
    • Hormone Binding Proteins: proteins that inactivate hormones, thus limiting bioactivity.
    • Epitope: an immunologically active site on a protein to which an antibody can attach.

    Endocrine Glands

    • Ductless, secrete products into extracellular fluids, then diffuse into blood.
    • Classical endocrine glands include pineal, hypothalamus, pituitary, thyroid, parathyroid, thymus, adrenal, pancreas, gonads (testes/ovaries).

    Hormone Release Mechanisms

    • Humoral: concentration of a solute (eg., glucose, calcium) detected by a gland, stimulating hormone release (eg., insulin, parathyroid hormone).
    • Neural: the nervous system directly stimulates hormone release (eg., sympathetic NS → adrenal medulla → catecholamines).
    • Hormonal: one hormone stimulates the release of another from a different cell (eg., hypothalamic hormones → anterior pituitary → other hormones).
    • Feedback Loops:
    • Ultra-short: secreted hormone feeds back to the same tissue that secreted it.
    • Short: secreted hormone feeds back to the tissue that stimulated its secretion.
    • Long: hormone secreted by the target organ feeds directly back to the hypothalamus.

    Endocrine Disorders

    • Level-of-Function Disorders:
    • Hypofunction: gland produces less than it should;
    • Common causes include loss of reserve, hypo-secretion, atrophy, and active destruction.
    • Hyperfunction: gland produces more than it should;
    • Common causes include hyper-secretion, hyperplasia, neoplastic change, and hyperstimulation.
    • Hierarchical Classification of Hypothalamo-Pituitary Axis Disorders:
    • Primary: disorder of the target gland.
    • Secondary: disorder of the pituitary gland.
    • Tertiary: disorder of the hypothalamus.
    • Testing for Endocrine Disorders:
    • Basal Hormone Testing: single snapshot measurement, problem is that some secretions are pulsatile, solution: dynamic hormone testing.
    • Dynamic Hormone Testing: using exogenous hormones to stimulate/suppress activity of a target gland.

    Levels of Feedback Loops

    • Ultra-short loop: secreted directly back to the producing tissues
    • Short loop: secreted hormones feed back to the tissues that stimulated the secretion; for ex, hormone secreting by the target organ feeds back to the pituitary.
    • Long loop: secreted hormone released by the target organ feeds back to the hypothalamus.

    Typical Endocrine Symptoms

    • Diabetes (Types 1 & 2)
    • Hyperthyroidism
    • Hypothyroidism
    • Polycystic Ovarian Syndrome (PCOS)
    • Cushing's Syndrome
    • Pituitary Adenoma
    • Acromegaly
    • Addison's Disease
    • Anorexia
    • Other relevant conditions

    Embryology of the Pituitary Gland

    • Anterior Pituitary: arises from an upward outpouching of the oral ectoderm (Rathke's pouch), composed of epithelial/glandular tissue, therefore manufactures and secretes hormones.
    • Posterior Pituitary: originates from a downward outpouching of neuroectoderm from the brain, consists of neural tissue, & therefore secretes neurohormones.

    Hypothalamus & Pituitary Glands

    • Hypothalamus: links the nervous system to the endocrine system, controls many bodily functions.
    • Pituitary: has two lobes - posterior and anterior, with distinct functions and embryologic origins.
    • Posterior Pituitary: composed of nervous tissue, secretes hormones like ADH and oxytocin.
    • Anterior Pituitary: is glandular tissue, controlled by hypothalamic releasing hormones.

    Blood Supply & Drainage of the Pituitary Gland

    • Arterial blood enters via hypophyseal branches of the internal carotid arteries.
    • Venous blood exits via venules draining into the dural sinuses.

    Regulation/Mechanism of Action of Thyroid Hormone (T3 and T4)

    • Thyroid Follicle Hyperplasia
    • ↑Iodine uptake from blood (Iodine Trapping)
    • ↑Thyroid Hormone synthesis
    • ↑Release of T3 & T4
    • Synthesis of Thyroid Hormone
    • Iodide uptake (Iodine Trapping); Iodide activation via oxidation; Secretion of activated iodine into colloid
    • Synthesis of thyroglobulin from tyrosines & secretion into colloid; lodination of tyrosine in colloid (forming DIT and MIT)
    • Hormone Release Mechanism
    • Thyroglobulin colloid is endocytosed + combined with lysosome.
    • Lysosomal enzymes cleave T3 &T4 from thyroglobulin; and unpaired DIT/MIT are released & deiodinised.
    • Released hormones diffuse into bloodstream (binding Proteins in the bloodstream).
    • Metabolic Effects of Thyroid Hormone: rapid response on heart, muscles, and many other organs
    • Regulation of Thyroid Hormone Production/Release
    • Hypothalamus secretes TRH (thyrotropin-releasing hormone) into portal circulation of pituitary.
    • TRH stimulates anterior pituitary to secrete TSH.
    • TSH stimulates the thyroid gland to secrete T4 and some T3.
    • T3 and T4 circulate in bloodstream, eliciting their effects, and providing negative feedback to the anterior pituitary.

    Metabolism – Insulin, Counter Regulatory Hormones, & Diabetes

    • Pancreas (99% acinar → exocrine cells): secrete digestive enzymes into GIT (duodenum) via pancreatic duct.
    • 1% are endocrine islet cells→
    • Alpha cells (25%): secrete glucagon.
    • Beta cells (60%): secrete insulin.
    • Delta cells (10%): secrete somatostatin.
    • PP cells (5%): secrete pancreatic polypeptide
    • Insulin is (only) the hypoglycaemic hormone. Incretins: intestinal hormones that ↑insulin secretion.
    • Counter-regulatory hormones: are hyperglycemic, they counter the effect of insulin (eg., glucagon, cortisol).
    • Insulin dependent tissues: liver, muscle, and adipose tissue – they're involved in nutrient processing/storage.
    • Insulin Independent tissues: Blood vessels, myocardium of the heart, nervous system, red blood cells, kidneys, and eyes

    Regulation of Insulin Secretion

    • Stimulators: Parasympathetic NS (rest & digestion), increased blood glucose and amino acids, GIP (Gastrointestinal Peptide), Glucagon,
    • Inhibitors: Sympathetic NS (fight or flight response), Somatostatin.

    Regulation of Glucagon Secretion

    • Stimulators: decreased blood glucose, amino acids, CCK, sympathetic NS.
    • Inhibitors: Insulin.

    Fluid & Electrolyte Balance

    • Regulation of Water Intake (Thirst)
    • ↓ Plasma volume → ↓ Blood flow to saliva glands → dry mouth → signals thirst center in hypothalamus.
    • ↑ Plasma osmolality directly causes cellular dehydration of osmoreceptors in hypothalamus → stimulates thirst center.
    • Regulation of Water Output:
    • Anti-diuretic Hormone (ADH) → ↓ Water Output:
    • ↑ Plasma osmolality → stimulation of osmoreceptors in hypothalamus
    • ↓ Plasma volume
    • ↑ Permeability of distal and collecting ducts →↑ permeability to water
    • Atrial Natriuretic Peptide (ANP) → ↑ Water Output
    • Acts to ↓blood volume & [Na⁺]
    • Secreted by atrial myocytes of the heart; Release in response to high blood pressure (atrial stretch)
    • Works by dilating afferent glomerular arteriole, constricting efferent glomerular arteriole → ↑filtration pressure → increased filtration →increased H₂O & Na⁺ excretion.
    • Inhibits Renin release →inhibits Renin-Angiotensin System
    • Inhibits Aldosterone Secretion →inhibits ADH Release

    Calcium & Phosphate Metabolism

    • Parathyroid glands (4 small endocrine glands, posterior surface of thyroid, size of a grain of rice) are the primary regulators of calcium homeostasis.
    • Chief cells of the parathyroid glands secrete parathyroid hormone (PTH).
    • PTH release is stimulated by ↓extracellular [Ca⁺], and inhibited by ↑extracellular [Ca⁺].
    • PTH aims to ↑plasma-Ca⁺ levels by increasing bone Ca⁺/P¯ resorption and ↓renal Ca⁺ excretion & ↑renal P¯ excretion.

    The 3 Major Hormones (Calcium & Phosphate)

    • Parathyroid Hormone (PTH):
    • Stimulated by low calcium levels, inhibits by high calcium levels.
    • Increases bone resorption, stimulates renal reabsorption of calcium, stimulates vitamin D3 synthesis and secretion
    • Increases intestinal absorption of calcium & phosphorus.
    • Vitamin D :
    • Stimulates intestinal absorption of calcium & phosphorus, and increases bone density.
    • Calcitonin
    • Stimulated by high calcium levels, inhibits bone resorption

    Stress & the Hypothalamo-Pituitary Axis

    • Stressors activate receptors, which inform the hypothalamus.
    • Hypothalamus activates sympathetic pathways and secretes corticotropin-releasing hormone (CRH).
    • CRH stimulates the anterior pituitary to release ACTH.
    • ACTH stimulates adrenal glands to release catecholamines (eg., adrenaline) and cortical steroids (eg., cortisol).

    General Adaptation Syndrome (GAS)

    • Stage 1: Alarm Reaction: immediate physical reaction to stress; preparing the body for life-threatening situations.
    • Stage 2: Resistance: the body adapts to sustained stress; maintains high levels of functioning.
    • Stage 3: Exhaustion: the body gives up and may experience sickness/death; ↓adaptive endocrine & neuroendocrine functions.

    The Body's Response to Stress

    • Stress triggers a response involving the limbic lobe and cerebral cortex → signals the hypothalamus → increased CRH & CRF → anterior pituitary → increased ACTH → adrenal glands secrete catecholamines & cortisol (and aldosterone).

    Reproductive Endocrinology

    • Hormonal Regulation of the Ovarian Cycle
    • Hypothalamus → GnRH → Anterior pituitary → FSH & LH → follicle growth, maturation & estrogen secretion (Positive Feedback) → corpus luteum develops & secretes progesterone/estrogen → inhibits FSH & LH (Negative Feedback).
    • Neuroendocrine Control: Hormonal Regulation of Spermatogenesis
    • Hypothalamus → GnRH → Anterior Pituitary → FSH & LH → sustaincular cells release ABP (androgen binding protein) which makes spermatogenic cells receptive to testosterone, and produces inhibin (negative feedback signal to hypothalamus).

    Types of Hormones

    • Tropic hormones: hormones that regulate the secretion of products by other endocrine glands (e.g. ACTH).
    • Non-tropic Hormones: hormones that regulate non-endocrine tissues.

    Gonadal Dysfunction

    • Male Hypogonadism: a deficiency in testosterone related to problems with either the testes or hypothalamus/pituitary.
    • Primary Hypogonadism: problem with Leydig cells in the testes → ↓ testosterone production → ↑ LH/FSH production.
    • Secondary Hypogonadism: problem with the hypothalamic-pituitary axis → ↓ LH/FSH release → ↓ testosterone production.

    Growth Dysfunction

    • Hyper: too much growth hormone or growth factors. Common examples include childhood gigantism and adult acromegaly.
    • Hypo: defective growth hormone axis; primary GH deficiency (hypothalamic or pituitary defect), or secondary pituitary deficiency (tumors or other destructive diseases).

    Multiple Endocrine Neoplasia Syndromes (MENs)

    • Familial endocrine neoplasias.
    • MEN disorders → ↑ risk of developing multiple cancerous or non-cancerous tumors in glands (parathyroid, pituitary, thyroid, adrenal).

    Thyroid Dysfunction

    • Hypothyroidism: insufficient thyroid hormone production; factors include autoimmune (Hashimoto's disease), dietary (iodine deficiency), and hypothalamic-pituitary disorders.
    • Hyperthyroidism: excessive thyroid hormone production; factors include autoimmune (Graves' disease), toxic multinodular goiter, or sub-acute thyroiditis.
    • Goiter: enlarged thyroid gland - can be non-toxic or toxic.

    Hypercalcemia / Hypocalcemia

    • Hypercalcemia: high calcium levels caused by various factors, including hyperparathyroidism, malignancy, and vitamin D excess.
    • Hypocalcemia: low calcium levels caused by factors like hypoparathyroidism, vitamin D deficiency, and chronic kidney failure.

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    Anatomy, Physiology & Pathology Notes of the Endocrine System PDF

    Description

    This quiz explores the intricate mechanisms involved in thyroid hormone synthesis and the relationship between various hormones in the Hypothalamic-Pituitary-Target axis. Test your understanding of the roles of thyroglobulin, T3, T4, and feedback loops. Perfect for students studying endocrinology or physiology.

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