The parathyroid hormone increases serum calcium and decreases serum phosphate. This consideration is:

Correct Answer: A

Rationale: Step 1: Parathyroid hormone (PTH) increases serum calcium levels by stimulating bone resorption and kidney reabsorption of calcium. Step 2: PTH decreases serum phosphate levels by promoting renal excretion of phosphate. Step 3: Therefore, the statement that PTH increases serum calcium and decreases serum phosphate is true. Step 4: Choice A is correct as it accurately reflects the actions of PTH. Step 5: Choices B, C, and D are incorrect as they do not accurately reflect the effects of PTH on serum calcium and phosphate levels.

Correct Answer: D

Rationale: The correct answer is D: Collecting duct. Spironolactone is a potassium-sparing diuretic that acts on the aldosterone receptor in the collecting duct of the nephron. This inhibits sodium reabsorption and potassium secretion, leading to increased excretion of sodium and water while retaining potassium. The other choices (A, B, C) are incorrect because spironolactone does not primarily act on the proximal convoluted tubule, ascending thick limb of the loop of Henle, or distal convoluted tubule.

Correct Answer: B

Rationale: The correct answer is B: Griseofulvin. Griseofulvin is used for dermatomycosis treatment because it is an antifungal medication specifically effective against dermatophytes. It works by disrupting the formation of fungal cell walls, leading to their destruction. Nystatin (A) is primarily used for yeast infections, not dermatomycosis. Amphotericin B (C) is a broad-spectrum antifungal, but it is not commonly used for dermatomycosis due to its potential side effects. Vancomycin (D) is an antibiotic effective against bacteria, not fungi. Therefore, the most appropriate choice for dermatomycosis treatment is Griseofulvin.

Correct Answer: D

Rationale: Step-by-step rationale for choosing Pyrimethamine (D) for toxoplasmosis treatment: 1. Pyrimethamine inhibits dihydrofolate reductase enzyme in Toxoplasma gondii. 2. This disrupts folate metabolism and impairs parasite growth. 3. Pyrimethamine is a standard treatment for toxoplasmosis. 4. Chloroquine (A) is used for malaria, Tetracycline (B) for bacterial infections, and Suramin (C) for African trypanosomiasis.

Correct Answer: D

Rationale: Step-by-step rationale: 1. Saquinavir is a protease inhibitor used to treat HIV/AIDS. 2. Protease inhibitors can cause gastrointestinal side effects like nausea, diarrhea, abdominal pain. 3. Saquinavir is known to induce rhinitis as a common side effect. 4. Options A, B, and C are antiviral drugs but do not typically cause these specific side effects. Summary: Saquinavir is the correct answer as it is a protease inhibitor known to induce gastrointestinal symptoms and rhinitis. The other options are antiviral drugs that do not have these specific side effects.