Endocrinology Practice Questions

Correct Answer: A

Rationale: The correct answer is A because parathyroid hormone does not directly stimulate osteoblasts to increase bone formation. Instead, it indirectly increases bone resorption by stimulating osteoclasts. Parathyroid hormone also increases calcium reabsorption from the distal tubule of the kidney (choice C) and inhibits phosphate reabsorption in the proximal tubule of the kidney (choice D). By understanding the physiological actions of parathyroid hormone, we can deduce that direct stimulation of osteoblasts is not one of its functions.

Correct Answer: C

Rationale: Sertoli cells are responsible for producing and secreting Androgen binding globulin (ABG). They play a crucial role in supporting spermatogenesis by providing structural and nutritional support to developing sperm cells. ABG helps in the transport of testosterone and other androgens within the seminiferous tubules, aiding in the regulation of spermatogenesis. Testosterone is primarily produced by Leydig cells in the testes, not by Sertoli cells, making option A incorrect. Option B, Oestrogen, is mainly synthesized in the ovaries, while Sertoli cells do not produce GnRH (option D), which is secreted by the hypothalamus. Therefore, the correct answer is C, as Sertoli cells are primarily responsible for producing and secreting Androgen binding globulin.

Correct Answer: C

Rationale: Rationale for choice C (FSH) being correct: 1. FSH stimulates Sertoli cells in the testes. 2. Sertoli cells produce androgen binding globulin (ABG). 3. ABG binds to testosterone, regulating its availability. 4. FSH indirectly influences testosterone levels via ABG production. Summary of incorrect choices: A. LH stimulates Leydig cells to produce testosterone, not Sertoli cells. B. GnRH regulates the release of FSH and LH but does not directly stimulate ABG production. D. Oxytocin is not involved in the regulation of Sertoli cells or ABG production in males.

Correct Answer: B

Rationale: The correct answer is B: Inhibition of the function of thyroid peroxidase. Propylthiouracil inhibits thyroid peroxidase, an enzyme essential for thyroid hormone synthesis. By blocking this enzyme, propylthiouracil reduces the production of thyroid hormones, helping to manage hyperthyroidism in Graves' disease. Explanation: 1. Propylthiouracil directly inhibits thyroid peroxidase, unlike other antithyroid medications that target different mechanisms. 2. Inhibition of thyroid peroxidase leads to decreased synthesis of thyroid hormones, effectively controlling hyperthyroidism. 3. Other choices are incorrect because propylthiouracil does not primarily affect the production of thyroid-stimulating immunoglobulins (choice A), peripheral conversion of T4 to T3 (choice C), or iodine organification (choice D) in the treatment of Graves' disease. In summary, the inhibition of thyroid peroxidase by

Correct Answer: B

Rationale: The correct answer is B: Weight loss. Hypothyroidism is characterized by an underactive thyroid gland, leading to a decreased metabolic rate. This typically results in weight gain, not weight loss. Choices A, C, and D are all associated with hypothyroidism. Loss of libido can occur due to hormonal imbalances, cardiac failure can result from the decreased metabolic rate affecting the heart, and organic psychosis can be a symptom of severe untreated hypothyroidism.