Androgen is secreted by

Correct Answer: C

Rationale: Androgens, mainly testosterone, are secreted by the testes' Leydig cells, activated by pituitary LH, making the testes the source. FSH regulates sperm, not androgens. GnRH from the hypothalamus triggers LH/FSH release, indirectly affecting androgens. The pituitary releases LH/FSH, not androgens. The testes' direct secretion role is fundamental, driven by LH, distinguishing it from regulatory hormones.

Correct Answer: A

Rationale: Antiseptics and disinfectants exert their bactericidal/bacteriostatic effects through various mechanisms, including:

Correct Answer: A

Rationale: The reticular activating system (RAS) in the brainstem regulates sleep-wake cycles, promoting alertness or rest, per neurophysiology. The cortex processes thought, not cycles. The limbic system drives emotion, not sleep directly. The cerebellum coordinates movement. RAS's role is central, controlling consciousness states.

Correct Answer: C

Rationale: The therapeutic range for Lithium is typically considered to be 0.6-1.2 mEq/L for maintenance treatment. However, some sources may also suggest a wider therapeutic range of 0.5-2 mEq/L. Monitoring serum lithium levels is crucial to ensure that the patient is within the therapeutic range and to adjust the dosage accordingly to avoid toxicity or subtherapeutic levels. Thus, option C (0.5-2) provides a more comprehensive and inclusive range that is commonly referenced in clinical practice.

Correct Answer: D

Rationale: Systolic hypertension (168 mmHg) in the elderly increases cardiovascular risk, despite normal diastolic (80 mmHg). Echo isn't first-line without organ damage signs (normal ECG). Reassurance ignores systolic risk; treatment is indicated (>160 mmHg). Doxazosin, an alpha-blocker, is less preferred initially due to hypotension risk. Ramipril, an ACE inhibitor, is effective, but amlodipine, a calcium channel blocker, is most appropriate per guidelines (e.g., NICE) for isolated systolic hypertension in the elderly, offering vascular protection and tolerability. Its efficacy reduces stroke and MI risk, critical at this age.

Correct Answer: D

Rationale: Isoniazid undergoes phase II acetylation via hepatic N-acetyltransferases, and the rate of metabolism can vary between slow and fast acetylators.

Correct Answer: D

Rationale: β2-agonist side effects (BP changes, nausea, hypomagnesemia) suggest overuse. Ipratropium , an anticholinergic bronchodilator, avoids these. Options , , persist with β2-agonists, risking side effects. Epinephrine (E) worsens them. Ipratropium's different mechanism improves asthma control safely.

Correct Answer: D

Rationale: Administration of leucovorin in the context of methotrexate treatment is known as rescue therapy. Leucovorin is used as a rescue agent to reduce the toxicity of methotrexate on normal cells. By providing leucovorin, which is a fully activated form of folic acid, the body can bypass the inhibition caused by methotrexate and continue with DNA base synthesis. This helps protect healthy cells and tissues from the toxic effects of methotrexate while allowing the chemotherapy to target and kill cancer cells. Rescue therapy with leucovorin is typically timed to occur after methotrexate administration to maximize its protective effects on normal cells.

Correct Answer: A

Rationale: Butoxamine (β2 antagonist) and terbutaline (β2 agonist) target the same receptor, a true pair. Phenoxybenzamine (α-adrenergic antagonist) and cyclopentolate (muscarinic antagonist) act on different receptors. Pilocarpine and bethanechol are both muscarinic agonists, not antagonist-agonist. Oxymetazoline (α-agonist) and dobutamine (β1-agonist) differ in receptor specificity. Bromocriptine and pramipexole are dopamine agonists. The β2 pair is a classic example in pharmacology, illustrating receptor-specific antagonism and agonism.