A patient presents with polyuria and thirst. There appears to be no elevation of glucose in the body, however, the serum osmolality appears to be low. Upon performing the water deprivation test, the osmolatity is still low. Which of the following is true?

Correct Answer: B

Rationale: The correct answer is B: The problem is in the kidneys. In this scenario, the low serum osmolality despite water deprivation indicates the kidneys are unable to concentrate urine, leading to excessive loss of water. This condition is known as nephrogenic diabetes insipidus. Choice A is incorrect as pituitary dysfunction would result in high serum osmolality due to lack of ADH. Choice C is incorrect as diabetes mellitus would show high glucose levels. Choice D is incorrect as high ADH in the serum would lead to concentrated urine and high serum osmolality.

Correct Answer: B

Rationale: The correct answer is B: antidiuretic hormone (ADH). ADH is released by the posterior pituitary gland to regulate water balance in the body by controlling the reabsorption of water in the kidneys. Thyroid hormone (A) is produced by the thyroid gland, while glucagon (C) and insulin (D) are produced by the pancreas to regulate blood sugar levels. ADH is the only hormone among the choices that is released by the posterior pituitary gland, making it the correct answer.

Correct Answer: A

Rationale: The correct answer is A: glucagon; liver. Alpha cells of the pancreas secrete glucagon, which targets the liver. Glucagon helps increase blood glucose levels by promoting glycogen breakdown in the liver. Melatonin is a hormone produced by the pineal gland, not the pancreas, and does not target the liver. Glucagon does not target the kidney, and calcitonin is produced by the thyroid gland and is involved in regulating calcium levels, not blood glucose levels.

Correct Answer: D

Rationale: The correct answer is D: adrenocorticotropic hormone (ACTH). ACTH is released by the pituitary gland in response to stress or low cortisol levels, stimulating the adrenal glands to release cortisol. Aldosterone (A) regulates electrolyte balance, angiotensin (B) regulates blood pressure, and antidiuretic hormone (C) regulates water balance, but they do not directly stimulate cortisol release. So, ACTH is the correct choice for stimulating cortisol production.

Correct Answer: A

Rationale: The correct answer is A because tropic hormones are hormones that regulate the function of other endocrine glands, such as ACTH (adrenocorticotropic hormone) and TSH (thyroid-stimulating hormone). These hormones stimulate the target glands to release their own hormones. Choice B is incorrect because tropic hormones specifically regulate other endocrine glands. Choice C is incorrect because tropic hormones typically exert their effects by binding to specific receptors on target cells, rather than directly activating genes. Choice D is incorrect because GH (growth hormone) and PRL (prolactin) are not tropic hormones as they do not directly regulate the function of other endocrine glands.