A deficiency of insulin causes:

Correct Answer: B

Rationale: The correct answer is B: hyperglycemia. Insulin deficiency leads to an inability to regulate blood sugar levels, resulting in elevated blood glucose levels. Without insulin, glucose cannot enter cells for energy utilization, leading to hyperglycemia. The other choices are incorrect because: A: Hypocalcemia is low calcium levels, not caused by insulin deficiency. C: Cushing syndrome is a hormonal disorder caused by prolonged exposure to high levels of cortisol, not related to insulin deficiency. D: Adrenal shock is a life-threatening condition due to insufficient adrenal gland function, not directly caused by insulin deficiency.

Correct Answer: C

Rationale: The correct answer is C: Thyroid. Iodine is essential for thyroid hormone production. A colloid is a gel-like substance found in the thyroid follicles. Goiter is a condition of thyroid enlargement. The other choices are incorrect because the pancreas (A) produces digestive enzymes and hormones like insulin, the parathyroid (B) regulates calcium levels, and the neurohypophysis (D) is part of the pituitary gland responsible for releasing hormones like vasopressin. Thus, the correct choice is the thyroid gland due to its association with iodine, colloid, and goiter.

Correct Answer: D

Rationale: Elevated plasma cortisol levels suppress the secretion of ACTH through negative feedback. High cortisol levels signal the hypothalamus and pituitary to decrease the release of CRH and ACTH, respectively, to maintain homeostasis. This is a regulatory mechanism to prevent excessive cortisol production. A: Elevated blood glucose levels do not directly suppress ACTH secretion. B: Dietary iodine is not related to ACTH secretion. C: CRH stimulates ACTH release, so it does not suppress its secretion.

Correct Answer: A

Rationale: Step-by-step rationale for why choice A is correct: 1. The adrenal cortex is indeed the target gland of ACTH (Adrenocorticotropic hormone). 2. ACTH stimulates the adrenal cortex to produce and release corticosteroid hormones. 3. These corticosteroid hormones play crucial roles in regulating metabolism, immune response, and stress response. 4. Therefore, choice A accurately describes the relationship between the adrenal cortex and ACTH. Summary: Choice A is correct because the adrenal cortex is the target gland of ACTH, not the other choices. The adrenal medulla secretes catecholamines (choice B), hormones that raise blood glucose (not lower, as in choice C), and iodine-containing hormones are secreted by the thyroid gland, not the adrenal cortex (choice D).

Correct Answer: D

Rationale: The correct answer is D because both Cushing syndrome and Addison's disease are disorders of the adrenal cortex. Cushing syndrome involves excessive cortisol production, while Addison's disease is characterized by insufficient cortisol production. Both conditions directly affect the adrenal cortex, leading to hormonal imbalances. Choice A is incorrect because Cushing syndrome involves hyperfunction, not hypofunction. Choice B is incorrect as it states hypersecretion, which is true for Cushing syndrome but not for Addison's disease. Choice C is incorrect because while replacement cortisol therapy is used for Addison's disease, it is not the only treatment option, and it does not apply to Cushing syndrome.