Which is false

Correct Answer: B

Rationale: Free cortisol feeds back negatively on both pituitary (ACTH) and hypothalamus (CRH) false to exclude hypothalamus. Suprachiasmatic nuclei drive ACTH's diurnal rhythm. Haemorrhage boosts aldosterone (RAAS) and cortisol (stress). Testosterone inhibits LH. Hypothalamic feedback distinguishes cortisol's regulation, key to HPA axis, unlike rhythm, stress, or gonadal truths.

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: D

Rationale: Local hormones and paracrine hormones act on nearby cells without bloodstream travel e.g., prostaglandins (local) or growth factors (paracrine). Autocrine hormones target the secreting cell, circulating hormones travel via blood (e.g., insulin). 'Both 1 and 2' (local and paracrine) fits, as both share this localized action. This distinguishes short-range endocrine signaling, key to tissue-specific responses like inflammation, contrasting with systemic hormone effects.

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.