Pituitary and Thyroid Physiology Practice Questions
40 free Pituitary and Thyroid Physiology practice questions for the Physiology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Which pituitary hormone is essential for somatic development after birth and for metabolism?
- A Growth hormone
- B Adrenocorticotropic hormone
- C Prolactin
- D Thyroid-stimulating hormone
Correct answer: Growth hormone
Growth hormone stimulates somatic growth and protein synthesis after birth. It also has important metabolic effects on carbohydrate and lipid metabolism.
Which thyroid hormone is present in the highest concentration in the circulation?
- A Triiodothyronine
- B Thyroxine
- C Reverse triiodothyronine
- D Calcitonin
Correct answer: Thyroxine
Thyroxine (T4) is the most abundant thyroid hormone in circulation. It serves mainly as a prohormone that is converted to T3 in peripheral tissues.
Which pituitary hormone directly stimulates thyroid hormone synthesis and release?
- A Growth hormone
- B Thyroid-stimulating hormone
- C Adrenocorticotropic hormone
- D Follicle-stimulating hormone
Correct answer: Thyroid-stimulating hormone
Thyroid-stimulating hormone acts on the thyroid gland to promote synthesis and secretion of T3 and T4. It is released from the anterior pituitary.
Which hormone inhibits thyroid-stimulating hormone release from the pituitary?
- A Thyroxine
- B Calcitonin
- C Iodide
- D Somatostatin
Correct answer: Somatostatin
Somatostatin inhibits the secretion of several pituitary hormones including TSH. It acts as a regulatory inhibitory hormone.
Which pituitary hormone is primarily responsible for milk ejection?
- A Prolactin
- B Oxytocin
- C Growth hormone
- D Thyroid-stimulating hormone
Correct answer: Oxytocin
Oxytocin causes contraction of myoepithelial cells in the mammary glands. This results in milk ejection during lactation.
Which thyroid hormone has the highest biological activity at the cellular level?
- A Thyroxine
- B Triiodothyronine
- C Reverse triiodothyronine
- D Calcitonin
Correct answer: Triiodothyronine
Triiodothyronine (T3) is the most biologically active thyroid hormone. It binds nuclear receptors with greater affinity than T4.
Which pituitary hormone stimulates cortisol secretion from the adrenal cortex?
- A Growth hormone
- B Thyroid-stimulating hormone
- C Adrenocorticotropic hormone
- D Luteinizing hormone
Correct answer: Adrenocorticotropic hormone
Adrenocorticotropic hormone stimulates the adrenal cortex to secrete cortisol. It plays a key role in the stress response.
Which cell type in the thyroid gland secretes calcitonin?
- A Follicular cells
- B Parafollicular cells
- C Parathyroid chief cells
- D Vascular endothelial cells
Correct answer: Parafollicular cells
Parafollicular cells, also known as C cells, secrete calcitonin. Calcitonin helps lower blood calcium levels.
Which hormone increases basal metabolic rate?
- A Calcitonin
- B Growth hormone
- C Thyroxine
- D Prolactin
Correct answer: Thyroxine
Thyroxine increases basal metabolic rate by enhancing cellular oxygen consumption. It affects nearly all tissues of the body.
Which pituitary hormone is secreted in response to suckling and promotes milk synthesis?
- A Oxytocin
- B Prolactin
- C Growth hormone
- D Thyroid-stimulating hormone
Correct answer: Prolactin
Prolactin stimulates milk synthesis in mammary glands. Its secretion is enhanced by suckling.
Which thyroid-related protein transports the majority of thyroid hormones in blood?
- A Serum albumin
- B Transthyretin (prealbumin)
- C Thyroxine-binding globulin
- D Corticosteroid-binding globulin
Correct answer: Thyroxine-binding globulin
Thyroxine-binding globulin carries most circulating T3 and T4. It has a high affinity for thyroid hormones.
Which pituitary hormone deficiency in childhood leads to dwarfism?
- A Thyroid-stimulating hormone
- B Growth hormone
- C Adrenocorticotropic hormone
- D Prolactin
Correct answer: Growth hormone
Growth hormone deficiency during childhood results in pituitary dwarfism. Linear growth is reduced but body proportions remain normal.
Which hormone mediates negative feedback on both the pituitary and hypothalamus in the thyroid axis?
- A Calcitonin
- B Iodide
- C Thyroxine
- D Somatostatin
Correct answer: Thyroxine
Thyroxine exerts negative feedback on both the pituitary and hypothalamus. This suppresses TSH and TRH secretion.
Which pituitary lobe releases antidiuretic hormone?
- A Anterior pituitary
- B Intermediate pituitary
- C Posterior pituitary
- D Pars tuberalis
Correct answer: Posterior pituitary
Antidiuretic hormone is released from the posterior pituitary. It regulates water balance by acting on the kidneys.
Which thyroid hormone effect explains heat intolerance in hyperthyroidism?
- A Reduced oxygen consumption
- B Increased basal metabolic rate
- C Decreased sympathetic activity
- D Reduced mitochondrial activity
Correct answer: Increased basal metabolic rate
Thyroid hormones increase basal metabolic rate and heat production. Excess hormone leads to heat intolerance.
Which pituitary hormone regulates gonadal function in both males and females?
- A Growth hormone
- B Thyroid-stimulating hormone
- C Gonadotropins
- D Prolactin
Correct answer: Gonadotropins
Gonadotropins, including LH and FSH, regulate gonadal function. They control gametogenesis and sex hormone secretion.
Which process in the thyroid gland requires iodine?
- A Secretion of calcitonin
- B Synthesis of thyroglobulin
- C Formation of thyroid hormones
- D Transport of hormones in blood
Correct answer: Formation of thyroid hormones
Iodine is essential for synthesis of T3 and T4. It is incorporated into tyrosine residues of thyroglobulin.
Which pituitary hormone excess causes gigantism when occurring before epiphyseal closure?
- A Prolactin
- B Growth hormone
- C Adrenocorticotropic hormone
- D Thyroid-stimulating hormone
Correct answer: Growth hormone
Excess growth hormone before epiphyseal closure results in gigantism. It leads to excessive linear growth.
Which thyroid hormone action is mediated by nuclear receptors?
- A Calcitonin
- B Thyroxine
- C Iodide
- D Thyroid-stimulating hormone
Correct answer: Thyroxine
Thyroxine acts via nuclear receptors after conversion to T3. This alters gene transcription and protein synthesis.
Which pituitary hormone is tonically inhibited by dopamine?
- A Growth hormone
- B Prolactin
- C Thyroid-stimulating hormone
- D Adrenocorticotropic hormone
Correct answer: Prolactin
Prolactin secretion is under tonic inhibitory control by dopamine. Reduction in dopamine increases prolactin release.
By what mechanism do hypothalamic releasing hormones, such as TRH, reach the anterior pituitary gland?
- A Retrograde axonal transport through the infundibulum
- B Diffusion through the cerebrospinal fluid of the third ventricle
- C The hypothalamic-hypophyseal portal venous system
- D Direct neural stimulation of the pars distalis
Correct answer: The hypothalamic-hypophyseal portal venous system
Hypothalamic hormones are secreted into the primary capillary plexus of the median eminence. They travel through the portal veins to the anterior pituitary, allowing for high local concentrations without systemic dilution.
A patient presents with low serum T4 and high serum TSH. Which of the following is the most likely location of the physiological defect?
- A Hypothalamus
- B Anterior pituitary
- C Thyroid gland
- D Peripheral tissues (resistance)
Correct answer: Thyroid gland
High TSH combined with low T4 indicates primary hypothyroidism, where the thyroid gland fails to produce hormone. The lack of negative feedback from T4 leads to the compensatory elevation of TSH from the pituitary.
The transport of iodide from the blood into the thyroid follicular cell occurs via the Sodium-Iodide Symporter (NIS). This is an example of which transport process?
- A Primary active transport
- B Secondary active transport
- C Facilitated diffusion (carrier)
- D Simple passive diffusion
Correct answer: Secondary active transport
The NIS utilizes the sodium gradient created by the Na+/K+ ATPase (primary active transport) to move iodide against its electrochemical gradient. This makes it a classic example of secondary active transport.
What is the 'Wolff-Chaikoff effect' in thyroid physiology?
- A Sudden release of stored hormone during physical trauma
- B Transient inhibition of hormone synthesis by high iodine
- C Rise in basal metabolic rate caused by excess circulating T3
- D Autoimmune destruction of thyroid peroxidase enzymes
Correct answer: Transient inhibition of hormone synthesis by high iodine
High levels of circulating iodide autoregulate the thyroid by acutely inhibiting the organification of iodine. This prevents the gland from producing excessive amounts of hormone in an iodine-rich environment.
Most of the growth-promoting effects of Growth Hormone (GH) are mediated by which peripheral signaling molecule?
- A Somatostatin (GH-inhibiting)
- B Insulin-like Growth Factor-1
- C Ghrelin (GH secretagogue)
- D Thyroxine (thyroid hormone)
Correct answer: Insulin-like Growth Factor-1
While GH has direct metabolic effects, its actions on bone and soft tissue growth are primarily mediated by IGF-1 (also known as Somatomedin C). IGF-1 is produced mainly in the liver in response to GH stimulation.
Which of the following would occur if the hypothalamic-pituitary stalk were surgically severed?
- A Decrease in every anterior pituitary hormone level
- B Increase in prolactin, drop in other anterior hormones
- C Increase in ADH alongside a decrease in oxytocin release
- D Decrease in prolactin with a rise in TSH secretion
Correct answer: Increase in prolactin, drop in other anterior hormones
Most anterior pituitary hormones rely on hypothalamic 'releasing' hormones, so their levels drop. Prolactin, however, is tonically inhibited by dopamine; removing this inhibition leads to an increase in Prolactin levels.
In peripheral tissues, the enzyme 5'-deiodinase is responsible for which critical step in thyroid hormone metabolism?
- A Inactivating T3 into T2
- B Converting T4 into the more potent T3
- C Converting T4 into the inactive reverse T3 (rT3)
- D Coupling monoiodotyrosine (MIT) and diiodotyrosine (DIT)
Correct answer: Converting T4 into the more potent T3
T4 is considered a pro-hormone with relatively low activity. 5'-deiodinase removes an iodine atom from the outer ring of T4 to create T3, which has a much higher affinity for nuclear thyroid receptors.
Central Diabetes Insipidus is characterized by a failure to secrete which hormone, and where is this hormone synthesized?
- A ADH; synthesized in the posterior pituitary
- B ADH; synthesized in the hypothalamus
- C Aldosterone; synthesized in the adrenal cortex
- D Oxytocin; synthesized in the hypothalamus
Correct answer: ADH; synthesized in the hypothalamus
Antidiuretic hormone (ADH) is synthesized in the supraoptic and paraventricular nuclei of the hypothalamus. It is then transported down axons to the posterior pituitary for storage and release.
Thyroid Stimulating Hormone (TSH) exerts its effects on follicular cells primarily through which secondary messenger system?
- A Inositol triphosphate (IP3) and DAG
- B Cyclic AMP (cAMP)
- C Cyclic GMP (cGMP)
- D Tyrosine kinase phosphorylation
Correct answer: Cyclic AMP (cAMP)
TSH binds to a G-protein coupled receptor on the thyroid follicular cell membrane. This activates adenylyl cyclase, increasing intracellular cAMP, which triggers iodine uptake and hormone synthesis.
Reverse T3 (rT3) is typically elevated in patients with 'Sick Euthyroid Syndrome.' How is rT3 produced?
- A Directly from the thyroid gland colloid
- B By deiodination of T4 at the 5-position (inner ring)
- C By deiodination of T3 at the 5'-position (outer ring)
- D By the coupling of two MIT molecules
Correct answer: By deiodination of T4 at the 5-position (inner ring)
rT3 is formed when T4 is deiodinated at the inner ring (5-position) rather than the outer ring. In states of severe illness or starvation, the body shunts T4 metabolism toward the inactive rT3 to conserve energy.
Which protein provides the tyrosine residues necessary for the synthesis of T3 and T4 within the thyroid follicle?
- A Thyroid Peroxidase (TPO)
- B Transthyretin
- C Thyroglobulin
- D Albumin
Correct answer: Thyroglobulin
Thyroglobulin is a large glycoprotein synthesized by follicular cells and secreted into the colloid. Iodine is attached to the tyrosine residues within the thyroglobulin molecule to form thyroid hormones.
What is the physiological effect of Growth Hormone (GH) on blood glucose levels?
- A Decreases blood glucose by increasing insulin sensitivity
- B Decreases blood glucose by inhibiting hepatic gluconeogenesis
- C Increases blood glucose via an anti-insulin effect on tissues
- D No effect on blood glucose; it only drives protein synthesis
Correct answer: Increases blood glucose via an anti-insulin effect on tissues
GH is a 'diabetogenic' hormone. It increases blood glucose by stimulating lipolysis and gluconeogenesis, and by decreasing the sensitivity of muscle and adipose tissue to insulin.
During the 'Ferguson reflex,' stretching of the cervix leads to a positive feedback loop involving which pituitary hormone?
- A Prolactin
- B Luteinizing Hormone (LH)
- C Oxytocin
- D Vasopressin
Correct answer: Oxytocin
Cervical stretch sends neural signals to the hypothalamus, triggering the release of oxytocin from the posterior pituitary. Oxytocin increases uterine contractions, which further stretches the cervix, amplifying the cycle until birth.
In Graves' Disease, hyperthyroidism is caused by which of the following?
- A Excessive secretion of TRH from the hypothalamus
- B A pituitary adenoma secreting TSH
- C Antibodies that bind to and activate the TSH receptor
- D Destruction of follicular cells releasing stored hormone
Correct answer: Antibodies that bind to and activate the TSH receptor
Graves' disease involves Thyroid-Stimulating Immunoglobulins (TSI). These autoantibodies mimic TSH and continuously stimulate the TSH receptor, leading to gland enlargement and excessive hormone production.
Which of the following hormones inhibits the release of Growth Hormone (GH) from the anterior pituitary?
- A Somatostatin
- B Ghrelin peptide
- C Dopamine
- D Arginine vasopressin
Correct answer: Somatostatin
Somatostatin (Growth Hormone Inhibiting Hormone) is produced in the hypothalamus. It acts on the pituitary to inhibit the secretion of both GH and TSH.
Where are the receptors for ADH (V2 receptors) located that mediate its primary antidiuretic effect?
- A Afferent arterioles of the renal glomerulus
- B Epithelial cells of the proximal convoluted tubule
- C Principal cells of the renal collecting duct
- D Smooth muscle cells lining systemic arterioles
Correct answer: Principal cells of the renal collecting duct
ADH binds to V2 receptors on the basolateral membrane of principal cells in the renal collecting ducts. This triggers the insertion of aquaporin-2 channels into the apical membrane to increase water reabsorption.
Thyroid peroxidase (TPO) is a multifunctional enzyme. Which of the following is NOT a role of TPO?
- A Oxidation of iodide to reactive iodine
- B Organification of iodine onto tyrosine residues of thyroglobulin
- C Coupling of iodotyrosines to form T3 and T4
- D Proteolysis of thyroglobulin to release free hormones
Correct answer: Proteolysis of thyroglobulin to release free hormones
TPO is responsible for oxidation, organification, and coupling. The release of free T3 and T4 from thyroglobulin, however, requires endocytosis of the colloid and subsequent proteolysis by lysosomal enzymes.
A patient has a large pituitary macroadenoma. Besides endocrine changes, they report losing their peripheral vision. This is due to compression of which structure?
- A Occipital lobe
- B Optic chiasm
- C Superior colliculus
- D Oculomotor nerve
Correct answer: Optic chiasm
The pituitary gland sits in the sella turcica, directly below the optic chiasm. Upward expansion of a tumor can compress the crossing fibers of the chiasm, resulting in bitemporal hemianopsia (loss of the outer half of both visual fields).
In a healthy individual, which of the following is the strongest stimulus for the release of ADH?
- A Increase in plasma osmolarity
- B Increase in mean arterial pressure
- C Decrease in plasma potassium levels
- D Decrease in blood pH
Correct answer: Increase in plasma osmolarity
Osmoreceptors in the hypothalamus are extremely sensitive to changes in plasma osmolarity. Even a 1% increase in osmolarity will trigger ADH release to conserve water and return osmolarity to normal.
Congenital hypothyroidism (Cretinism) leads to profound intellectual disability and stunted growth because thyroid hormones are essential for:
- A Closure of the epiphyseal plates
- B Development of the CNS and myelination
- C Synthesis of hemoglobin in the fetus
- D Regulation of core body temperature in utero
Correct answer: Development of the CNS and myelination
Thyroid hormones are critical during the perinatal period for brain development, including dendrite branching and myelin formation. Without early replacement therapy, the damage to the central nervous system is irreversible.