Cortisol is produced by the:

Correct Answer: A

Rationale: The correct answer is A: adrenal cortex. Cortisol is a glucocorticoid hormone produced by the adrenal cortex. The adrenal cortex is responsible for the synthesis and secretion of cortisol in response to stress. The adrenal medulla produces catecholamines like adrenaline and noradrenaline, not cortisol. The anterior pituitary produces adrenocorticotropic hormone (ACTH), which stimulates cortisol production by the adrenal cortex. The pancreas produces insulin and glucagon, not cortisol. Therefore, the adrenal cortex is the correct choice for the production of cortisol.

Correct Answer: B

Rationale: The correct answer is B: Androgens. Androgens are male sex hormones responsible for male characteristics like facial hair growth and deepening of voice. Aldosterone (A) is a mineralocorticoid hormone, not a sex hormone. Pheromones (C) are chemical signals, not hormones. Insulin (D) is a hormone that regulates blood sugar levels, not related to sex characteristics. Therefore, B is the correct choice for a male sex hormone.

Correct Answer: D

Rationale: The correct answer is D: Parathyroid hormone. Parathyroid hormone plays a crucial role in regulating calcium homeostasis by increasing calcium levels in the blood through various mechanisms. It promotes calcium release from bones, enhances calcium absorption in the intestines, and reduces calcium excretion from the kidneys. Insulin (Choice A) primarily regulates blood sugar levels, not calcium. Erythropoietin (Choice B) stimulates red blood cell production and does not directly affect calcium homeostasis. Aldosterone (Choice C) regulates sodium and potassium balance but not calcium levels. Thus, Parathyroid hormone is the correct choice for controlling calcium homeostasis.

Correct Answer: C

Rationale: The correct answer is C: luminal acid. Gastrin secretion is primarily stimulated by the presence of luminal peptides and vagal discharge. Luminal acid inhibits gastrin secretion through negative feedback mechanisms. Phenylalanine does not directly stimulate gastrin secretion. In summary, luminal acid is the correct answer because it acts as an inhibitory factor for gastrin secretion, whereas the other choices are known stimulatory factors.

Correct Answer: D

Rationale: The correct answer is D. Folate absorption is not Na+ dependent because it is absorbed in the small intestine through a carrier-mediated process independent of sodium. Thiamin, riboflavin, and niacin require sodium-dependent transport mechanisms for absorption in the small intestine. Thiamin is absorbed through thiamin transporters that are Na+ dependent. Riboflavin is absorbed by sodium-dependent multivitamin transporters. Niacin absorption also involves sodium-dependent transporters. Therefore, folate is the only option that is not Na+ dependent for absorption.