Endocrinology Practice Questions

Correct Answer: C

Rationale: The correct answer is C: Purple skin striae. This is the most common sign of Cushing's syndrome due to the excessive production of cortisol leading to thinning of the skin and formation of purple stretch marks. Hirsutism (A) is excessive hair growth, not specific to Cushing's. Obesity (B) can be a symptom, but it is not the most common. Skin hyperpigmentation (D) is seen in Addison's disease, not Cushing's.

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: The correct answer is C: Glucose-6-phosphatase deficiency. This enzyme is essential for gluconeogenesis and glycogenolysis, so its deficiency leads to fasting hypoglycemia. Galactosaemia (A) can cause hypoglycemia due to impaired galactose metabolism. Insulinoma (B) results in excess insulin production causing hypoglycemia. Systemic carnitine deficiency (D) can lead to hypoglycemia by impairing fatty acid oxidation, but it does not directly cause fasting hypoglycemia as seen in Glucose-6-phosphatase deficiency.

Correct Answer: A

Rationale: The correct answer is A: Cirrhosis. In cirrhosis, there is a decrease in the binding proteins for T4, leading to decreased total T4 levels in the plasma. Pregnancy, euthyroid sick syndrome, and familial excess thyroid binding globulin are all conditions associated with increased total T4 levels due to various physiological changes. In pregnancy, there is an increase in thyroid hormone production to support fetal development. Euthyroid sick syndrome is a condition where there is a decrease in binding proteins, leading to an increase in free T4 levels but normal total T4 levels. Familial excess thyroid binding globulin causes an increase in total T4 levels due to excessive binding proteins.

Correct Answer: C

Rationale: The correct answer is C: Myxoedema. Myxoedema is associated with hypothyroidism, not SIADH. Guillain-Barre syndrome, subacute bacterial endocarditis, and bronchogenic carcinoma are all conditions that can lead to SIADH due to various mechanisms. Guillain-Barre syndrome can cause SIADH through autonomic dysfunction, endocarditis through the release of inflammatory cytokines, and bronchogenic carcinoma through production of ectopic ADH. Therefore, myxoedema is the only incorrect choice as it does not typically lead to SIADH.