regarding Ca metabolism

Correct Answer: C

Rationale: Oestrogen inhibits osteoclasts, reducing bone resorption, preserving mass post-menopause osteoporosis link. Ca is ~1-2% body mass, not 15%. Intestinal Ca absorption is active (vitamin D), not passive. Corticosteroids inhibit osteoblasts, promoting loss. Oestrogen's osteoclast suppression distinguishes it, key to bone health, unlike mass, absorption, or steroid errors.

Correct Answer: C

Rationale: An antagonistic effect occurs when one hormone opposes another e.g., insulin lowers glucose, glucagon raises it not synergistic (cooperative), permissive (enabling), circulating (delivery), or local (proximity). This opposition distinguishes endocrine balance, vital for homeostasis, contrasting with cooperative or static effects.

Correct Answer: A

Rationale: Insulin from pancreatic beta cells lowers blood glucose by promoting uptake and storage, unlike glucagon (raises glucose), somatostatin (inhibits), or thyroid/calcitonin (metabolism/calcium). This distinguishes insulin's hypoglycemic action, key to diabetes management, contrasting with opposing or unrelated hormones.

Correct Answer: A

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: C

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.