The vitamin that is regarded to be a hormone is

Correct Answer: A

Rationale: Vitamin D acts as a hormone, regulating calcium via its active form.

Correct Answer: A

Rationale: Potassium iodide increases bronchial secretions, used in respiratory conditions.

Correct Answer: A

Rationale: Etidronate treats Paget's disease and hypercalcaemia by inhibiting bone turnover. Its oral bioavailability is low, and it's not typically used with calcium for osteoporosis.

Correct Answer: B

Rationale: Sulphonylureas relieve polyuria/polydipsia by lowering glucose and require beta cells to stimulate insulin release. They're not for ketosis-prone patients, vascular benefits are unproven, and dosing varies.

Correct Answer: C

Rationale: Sildenafil, an oral PDE5 inhibitor, enhances erection and causes side effects like headaches and blue vision. It's contraindicated with nitrates due to hypotension risk.