Which of the following structures connects the hypothalamus and the adenohypophysis?

Correct Answer: B

Rationale: The correct answer is B: Portal capillaries. The hypothalamus and adenohypophysis are connected by a system of blood vessels called the hypothalamic-pituitary portal system, which includes portal capillaries. These capillaries carry releasing and inhibiting hormones from the hypothalamus to the adenohypophysis to regulate the secretion of pituitary hormones. The other choices are incorrect because: A: Islets of Langerhans are clusters of cells in the pancreas involved in insulin and glucagon production, not connected to the hypothalamus or adenohypophysis. C: The corpus callosum is a structure that connects the two cerebral hemispheres and is not related to the hypothalamus or adenohypophysis. D: The medulla oblongata is part of the brainstem responsible for autonomic functions and is not involved in connecting the hypothalamus and adenohypophysis.

Correct Answer: C

Rationale: Rationale: 1. Myxedema is caused by hypothyroidism, which can be effectively treated with thyroxine. 2. Thyroxine is a synthetic form of thyroid hormone that helps restore thyroid hormone levels. 3. Myxedema symptoms such as fatigue, weight gain, and cold intolerance improve with thyroxine treatment. Summary of Incorrect Choices: A. Diabetes mellitus and hyperglycemia are not directly related to thyroid hormone levels. B. Hyperglycemia is not primarily treated with thyroxine. D. Graves' disease is a thyroid disorder characterized by hyperthyroidism, which requires different treatments than hypothyroidism.

Correct Answer: D

Rationale: Step-by-step rationale: 1. Hypocalcemic tetany results from low blood calcium levels. 2. Parathyroid hormone (PTH) regulates calcium levels by increasing calcium release from bones and reabsorption in the kidneys. 3. A deficiency in parathyroid activity leads to decreased calcium levels, causing tetany. 4. Choice D is correct as it directly links hypocalcemic tetany to parathyroid dysfunction. Summary: A: Incorrect, calcitonin lowers blood calcium levels. B: Incorrect, TSH regulates thyroid function, not calcium levels. C: Incorrect, osteoclasts break down bone tissue but are not directly related to hypocalcemic tetany.

Correct Answer: A

Rationale: The correct answer is A: Adrenal medulla. The adrenal medulla secretes adrenaline and noradrenaline, which are hormones that enhance the sympathetic response of the body. This response includes increased heart rate, dilation of airways, and increased blood flow to muscles. The other choices, B: Pancreas, C: Adrenal cortex, and D: Parathyroid, do not directly enhance sympathetic responses. The pancreas regulates blood sugar levels, the adrenal cortex produces cortisol and aldosterone, and the parathyroid regulates calcium levels. Therefore, only the adrenal medulla directly contributes to the sympathetic response, making it the correct choice.

Correct Answer: C

Rationale: The correct answer is C: Replacement dose of thyroid hormones. In newly diagnosed cretinism, there is a deficiency of thyroid hormones, leading to developmental delays and other health issues. Administering replacement thyroid hormones is crucial to normalize hormone levels and support proper growth and development. Thyroidectomy (choice A) is not necessary in this case as the goal is to supplement the missing hormones. Option B, the administration of radioactive iodine cocktail, is used to treat hyperthyroidism, not hypothyroidism. Choice D, replacement dose of calcitonin, is not relevant as calcitonin is involved in calcium regulation, not thyroid hormone production. Thus, the most critical need for the child with newly diagnosed cretinism is the replacement dose of thyroid hormones to address the underlying hormonal deficiency.