In the thyroid

Correct Answer: D

Rationale: Thyroglobulin is synthesized in thyroid follicular cells (rough ER), secreted into colloid for iodination, not formed there key to T3/T4 production. Iodide transport is active (Na⁺/I⁻ symporter). Reverse T3 (rT3) is inert. Most T4 converts to T3 peripherally. Thyroglobulin's cellular origin distinguishes it, critical for thyroid synthesis, unlike transport, activity, or metabolism truths.

Correct Answer: C

Rationale: Noradrenaline (via α2-receptors) inhibits insulin secretion, prioritizing glucose mobilization in stress. Mannose (metabolized like glucose), glucagon (short-term β-cell boost), and leucine (amino acid trigger) stimulate insulin. Noradrenaline's suppression distinguishes it, critical for sympathetic-glucose balance, unlike stimulatory sugars, hormones, or amino acids.

Correct Answer: B

Rationale: Prolactin from the anterior pituitary triggers milk production in mammary glands, not LH (ovulation), thyrotropin (thyroid), MSH (pigmentation), or ACTH (cortisol). Its specific lactogenic role distinguishes it, vital for postpartum nutrition, contrasting with reproductive or stress hormones.

Correct Answer: D

Rationale: Calcitriol (active vitamin D) raises blood calcium by enhancing absorption, though not a thyroid hormone calcitonin (thyroid-produced) lowers it, while T3/T4 regulate metabolism, TRH/TSH stimulate thyroid. Context suggests calcitonin intent, but 'D' (calcitriol) aligns with calcium regulation broadly. This distinguishes calcium homeostasis, vital for bone and nerve function, contrasting with thyroid's metabolic focus.

Correct Answer: D

Rationale: Parathyroid glands (often labeled 'E' in diagrams) secrete PTH to raise blood calcium, unlike thyroid (calcitonin, lowers) or others. 'E' aligns with prior answer. This distinguishes PTH's role in calcium homeostasis, vital for nerve and bone function, contrasting with metabolic glands.