With respect to the thyroid gland which is false

Correct Answer: C

Rationale: T4's action is slower than T3's converted to T3 for potency, acting via nuclear receptors over hours. Iodide is actively transported into colloid for synthesis. MIT/DIT (intermediates) aren't secreted only T3/T4. TBG, not albumin, binds most T4 albumin has capacity but lower affinity. Slower T4 action distinguishes it, key to thyroid kinetics, unlike transport, secretion, or binding truths.

Correct Answer: D

Rationale: High plasma Ca²⁺ reduces 1,25-dihydroxycholecalciferol (active vitamin D) via feedback, inhibiting renal 1α-hydroxylase balances absorption. ~99% filtered Ca is reabsorbed, not 60%. GIT Ca absorption is active (vitamin D-dependent), not mainly passive. Ca binding is proportional to protein levels (e.g., albumin), not inverse. Vitamin D reduction distinguishes it, key to Ca homeostasis, unlike reabsorption, absorption, or binding errors.

Correct Answer: B

Rationale: Somatostatin inhibits insulin secretion from β-cells, reducing glucose uptake regulatory role. Insulin promotes protein synthesis, not catabolism anabolic. Phenytoin doesn't notably stimulate insulin glucose metabolism does. Insulin increases K⁺ uptake with glucose, not decreases. Somatostatin's inhibition distinguishes it, key to pancreatic regulation, unlike anabolic, drug, or K⁺ errors.

Correct Answer: B

Rationale: Adrenocorticotropic hormone (ACTH) from the anterior pituitary stimulates cortisol secretion from the adrenal cortex, key to stress response not LH, prolactin, IGFs (GH mediators), or MSH. ACTH's role in the HPA axis distinguishes it, critical for glucocorticoid regulation, contrasting with unrelated hormones.

Correct Answer: D

Rationale: T3 and T4 synthesis involves iodide trapping, oxidation to iodine, tyrosine iodination, and coupling not calcitonin synthesis, which occurs in separate thyroid C-cells for calcium regulation. This exclusion distinguishes thyroid hormone production, essential for metabolism, from unrelated calcitonin processes.