Commonest enzymatic defect for development of congenital adrenal hyperplasia is:

Correct Answer: A

Rationale: C-21 hydroxylase deficiency is the most common enzymatic defect leading to the development of congenital adrenal hyperplasia (CAH). This enzyme is necessary for the synthesis of cortisol and aldosterone in the adrenal glands. When there is a deficiency in C-21 hydroxylase, the pathway is shifted towards the production of androgens instead of cortisol and aldosterone, leading to excess androgen production. This results in the characteristic features of CAH, such as ambiguous genitalia in females and virilization in both males and females. Other enzyme deficiencies listed in the choices can also lead to different types of CAH but are less common compared to C-21 hydroxylase deficiency.

Correct Answer: D

Rationale: Vanillylmandelic acid (VMA) is a metabolite of catecholamines, such as epinephrine and norepinephrine. Phaeochromocytoma is a catecholamine-secreting tumor that arises from the chromaffin cells in the adrenal medulla or sympathetic ganglia. As a result of the increased production of catecholamines in patients with phaeochromocytoma, there is an increase in VMA excretion in the urine. This increase in VMA excretion is a significant diagnostic feature of phaeochromocytoma and helps in its detection through urine testing. Therefore, the correct choice is D. Phaeochromocytoma.

Correct Answer: D

Rationale: Charcot joint, also known as neuropathic arthropathy, is a serious complication of diabetes mellitus that affects the joints. It commonly affects the foot, especially the midfoot and hindfoot. The condition is characterized by joint deformities, fractures, and dislocations due to nerve damage and loss of sensation in the foot. The repetitive stress on the foot from walking or weight-bearing activities can lead to progressive joint destruction and deformity. It is important for individuals with diabetes to monitor their foot health closely and seek prompt medical attention if they notice any changes or deformities in their feet.

Correct Answer: C

Rationale: The prolonged ingestion of iodine causing goiter is known as the Wolf-Chaikoff effect. This phenomenon occurs when high levels of iodine cause a temporary inhibition of thyroid hormone synthesis, resulting in a decrease in thyroid hormone production. In some individuals, this can lead to the development of a goiter due to the lack of thyroid hormone feedback regulation. It is important to note that the Wolf-Chaikoff effect typically resolves on its own as the thyroid gland adapts to the increased iodine levels over time.

Correct Answer: B

Rationale: Karyotype 47, XYY refers to the presence of an extra Y chromosome in males. This condition is known as XYY syndrome, also called Jacob's syndrome. Individuals with XYY syndrome are typically phenotypically male but may have some associated physical and behavioral characteristics. These individuals are often referred to as "supermales" due to the presence of the extra Y chromosome. This is different from true hermaphroditism, Klinefelter's syndrome, and gonadal dysgenesis, which have distinct chromosomal patterns and manifestations.