Which of the following organs is affected by thyroid hormone in adults?

Correct Answer: A

Rationale: The correct answer is A: liver. Thyroid hormone affects the liver by regulating metabolism and energy production. It increases the breakdown of fats, proteins, and carbohydrates. The liver plays a crucial role in converting thyroid hormones into their active form. Summary: B: The spleen is not directly affected by thyroid hormone. C: The thyroid gland produces thyroid hormone but is not directly affected by it in adults. D: While the brain is indirectly influenced by thyroid hormone, it is not a primary target organ for its effects in adults.

Correct Answer: C

Rationale: The correct answer is C: growth hormone and LH. The anterior pituitary gland secretes these hormones. Growth hormone regulates growth, metabolism, and body composition, while LH (luteinizing hormone) plays a role in reproductive function. A: Anti-diuretic hormone and oxytocin are produced by the posterior pituitary gland. B: ACTH (adrenocorticotropic hormone) is secreted by the anterior pituitary, but insulin is produced by the pancreas. D: Thyroxine is released by the thyroid gland, and cortisol is produced by the adrenal glands, not the anterior pituitary.

Correct Answer: D

Rationale: The correct answer is D: parathyroid hormone. Calcitonin and parathyroid hormone regulate calcium levels in the blood. Calcitonin lowers blood calcium levels by inhibiting bone resorption, while parathyroid hormone increases blood calcium levels by promoting bone resorption. Thus, they have opposite effects on calcium regulation, making parathyroid hormone the antagonistic hormone to calcitonin. Thyroxine (A), growth hormone (B), and insulin (C) do not directly oppose the action of calcitonin in regulating calcium levels.

Correct Answer: C

Rationale: The correct answer is C: glucagon. Glucagon is the hormone that opposes the actions of insulin by increasing blood glucose levels. When blood sugar levels are low, glucagon signals the liver to release stored glucose, raising blood sugar levels. Cortisol (A) and mineralocorticoids (D) are not directly antagonistic to insulin. Norepinephrine/epinephrine (B) play a role in the fight-or-flight response, but they do not directly counteract insulin's actions on glucose regulation.

Correct Answer: D

Rationale: The correct answer is D: Increases blood calcium level. Parathormone is released by the parathyroid glands in response to low blood calcium levels. It acts to increase blood calcium levels by stimulating the release of calcium from bones, increasing calcium absorption in the intestines, and promoting calcium reabsorption in the kidneys. This helps to maintain proper calcium levels in the body. Choices A, B, and C are incorrect because parathormone does not have any direct effect on blood sodium levels and actually works to increase, not decrease, blood calcium levels.