Which of the following hormones are released in response to decreases in blood glucose concentration?

Correct Answer: C

Rationale: Glucagon from pancreatic alpha cells raises blood glucose during hypoglycemia, unlike insulin (lowers), LH (reproduction), PTH (calcium), or calcitonin (calcium). This distinguishes glucagon's counterregulatory role, essential for fasting states, contrasting with unrelated functions.

Correct Answer: A

Rationale: Aldosterone increases Na+ and water reabsorption, raising blood volume reduces urine indirectly, not lowers pressure. 'A' inferred. This distinguishes aldosterone's hypertensive role, key to fluid balance, contrasting with diuretic effects.

Correct Answer: C

Rationale: Pineal gland (contextual) produces melatonin for sleep, not testosterone (gonads), glucagon (pancreas), thymopoietin (thymus), or vasopressin (pituitary). This distinguishes melatonin's role, key to circadian rhythms, contrasting with reproductive or immune hormones.

Correct Answer: D

Rationale: PTH (calcium drop), insulin (glucose rise), and glucagon (glucose drop) all respond to blood chemistry changes 'all' fits. This distinguishes endocrine responsiveness, critical for homeostasis, contrasting with static or neural triggers.

Correct Answer: A

Rationale: Glucagon targets liver hepatocytes for glycogenolysis, not pancreas (secretion site) or muscle (lacking receptors). 'A' inferred. This distinguishes glucagon's hepatic role, vital for glucose release, contrasting with insulin's broader targets.