ACTH ________.

Correct Answer: B

Rationale: Correct Answer: B - Secretion of ACTH is regulated by a hypothalamic secretion. Rationale: 1. The hypothalamus secretes corticotropin-releasing hormone (CRH). 2. CRH stimulates the anterior pituitary to release adrenocorticotropic hormone (ACTH). 3. ACTH then stimulates the adrenal cortex to release cortisol. 4. This feedback loop demonstrates how ACTH secretion is regulated by a hypothalamic secretion. Summary: A - Incorrect. ACTH is secreted by the anterior pituitary, not the posterior pituitary. C - Incorrect. ACTH causes the release of hormones from the adrenal cortex, not the adrenal medulla. D - Incorrect. ACTH is a tropic hormone as it acts on another endocrine gland (adrenal cortex).

Correct Answer: B

Rationale: The correct answer is B: anterior pituitary gland. The hypothalamus secretes releasing and inhibiting hormones that travel to the anterior pituitary gland through the hypophyseal portal system, where they regulate the production and secretion of various hormones. This control mechanism ensures proper hormonal balance in the body. Choices A, C, and D are incorrect because the adrenal cortex, posterior pituitary gland, and thyroid gland are not directly regulated by the hypothalamus through releasing and inhibiting hormones.

Correct Answer: D

Rationale: The correct answer is D: Thyroid gland. The thyroid gland requires iodine to produce its hormones, such as thyroxine and triiodothyronine, which are essential for regulating metabolism, growth, and development. Iodine is a crucial component of these thyroid hormones. The other choices (A: Adrenal cortex, B: Pancreas, C: Parathyroid glands) do not require iodine for hormone production and are not involved in the synthesis of thyroid hormones. Therefore, the correct answer is the thyroid gland because it specifically relies on iodine for hormone synthesis, making it the only gland in the list that fits this criteria.

Correct Answer: D

Rationale: The correct answer is D: aldosterone. Aldosterone is the main mineralocorticoid produced by the adrenal cortex, responsible for regulating electrolyte balance and blood pressure. It acts on the kidneys to increase sodium reabsorption and potassium excretion. Cortisol (A) is a glucocorticoid, not a mineralocorticoid. Glucagon (B) is a hormone produced by the pancreas that raises blood glucose levels. Epinephrine (C) is a hormone produced by the adrenal medulla involved in the fight-or-flight response, not a mineralocorticoid. Therefore, the correct answer is aldosterone (D) due to its specific role in mineral balance regulation.

Correct Answer: B

Rationale: The correct answer is B because estrogen is indeed necessary for the maturation of the ovum. Estrogen promotes the development and release of the egg from the ovary during the menstrual cycle. This hormone is crucial for the growth of the follicles in the ovary and prepares the uterus for potential pregnancy. Rationale: A: Progesterone is responsible for maintaining the uterine lining during pregnancy, not for female secondary sex characteristics. C: Estrogen plays a significant role in breast development, so this statement is incorrect. D: Progesterone helps to prepare the uterus for pregnancy by promoting the growth of the uterine lining, not the uterus itself.