Endocrinology Practice Questions

Correct Answer: D

Rationale: The correct answer is D: Thyroxine-binding globulin (TBG). TBG is the primary source of bound T4 in the plasma as it specifically binds to and transports thyroid hormones. This protein has the highest affinity for T4 compared to other plasma proteins. Albumin (A) and gamma globulins (B) can also bind to thyroid hormones, but TBG is the primary carrier. Thyroid peroxidase (C) is an enzyme involved in thyroid hormone production, not in binding T4 in the plasma.

Correct Answer: D

Rationale: The correct answer is D because the anterior pituitary is regulated by hypothalamic neuropeptides. The hypothalamus secretes releasing and inhibiting hormones that control the anterior pituitary's hormone release. This close interaction between the hypothalamus and the anterior pituitary is known as the hypothalamic-pituitary axis. A is incorrect because the anterior pituitary is not neural tissue, it is an endocrine gland. B is incorrect because the anterior pituitary synthesizes and secretes peptide hormones, not steroid hormones. C is incorrect because the anterior pituitary is located at the base of the brain, not above the kidney.

Correct Answer: C

Rationale: The correct answer is C: Ischaemic heart disease. Metabolic syndrome X consists of a cluster of conditions, including hyperlipidemia, obesity, hypertension, and insulin resistance. Ischaemic heart disease, while commonly associated with metabolic syndrome X due to the increased risk factors, is not a direct component of the syndrome itself. Therefore, it is not considered a part of metabolic syndrome X. Hyperlipidemia (A), obesity (B), and hypertension (D) are all key components of metabolic syndrome X due to their association with insulin resistance and increased risk of cardiovascular disease.

Correct Answer: B

Rationale: The correct answer is B: Cretinism. Cretinism is the most common cause of preventable mental deficiency worldwide due to severe iodine deficiency during pregnancy. Iodine is crucial for thyroid hormone production, which is essential for fetal brain development. Beriberi disease (A) is caused by thiamine deficiency and affects the nervous system, not mental deficiency. Folate deficiency (C) can cause neural tube defects but not mental deficiency. Vitamin A deficiency (D) can lead to blindness and immune system issues, but not the most common cause of preventable mental deficiency.

Correct Answer: B

Rationale: The correct answer is B: Intranasal vasopressin may be helpful. In diabetes insipidus, there is a deficiency of vasopressin leading to excessive urination and thirst. Administering vasopressin intranasally can help replace the deficient hormone, reducing urine output and thirst. Hypernatremia (choice A) can occur due to excessive water loss, but it is not always present. There is no osmolar gap (choice C) in diabetes insipidus. Urine specific gravity (choice D) is typically low in diabetes insipidus due to the dilute urine produced.