The diagnostic marker for 21-hydroxylase deficiency in congenital adrenal hyperplasia is elevated which substance?

The diagnostic marker for 21-hydroxylase deficiency in congenital adrenal hyperplasia is elevated which substance?

• A. Progesterone
• B. 17-Hydroxyprogesterone
• C. Cortisol
• D. DHEA

Answer: (B)

In 21-hydroxylase deficiency, the block is right at the step that converts 17-hydroxyprogesterone to 11-deoxycortisol, which is part of cortisol synthesis. Because this step can’t proceed, 17-hydroxyprogesterone accumulates, and the pituitary pumps out more ACTH to try to drive production, leading to even higher levels of this precursor. That buildup makes elevated 17-hydroxyprogesterone the most reliable diagnostic marker for this form of congenital adrenal hyperplasia. Cortisol is typically low, not high; DHEA can be increased due to androgen excess but isn’t specific to this defect; progesterone might rise as well but doesn’t identify the exact block. In practice, a high 17-hydroxyprogesterone level prompts confirmation with an ACTH stimulation test to assess the cortisol response.

In 21-hydroxylase deficiency, the block is right at the step that converts 17-hydroxyprogesterone to 11-deoxycortisol, which is part of cortisol synthesis. Because this step can’t proceed, 17-hydroxyprogesterone accumulates, and the pituitary pumps out more ACTH to try to drive production, leading to even higher levels of this precursor. That buildup makes elevated 17-hydroxyprogesterone the most reliable diagnostic marker for this form of congenital adrenal hyperplasia. Cortisol is typically low, not high; DHEA can be increased due to androgen excess but isn’t specific to this defect; progesterone might rise as well but doesn’t identify the exact block. In practice, a high 17-hydroxyprogesterone level prompts confirmation with an ACTH stimulation test to assess the cortisol response.