In a patient with 21-hydroxylase deficiency, which steroid is likely to be increased?

In the context of 21-hydroxylase deficiency, 17-hydroxyprogesterone is indeed the steroid that is most likely to be increased. This condition is a form of congenital adrenal hyperplasia (CAH) caused by a deficiency in the enzyme 21-hydroxylase, which is critical for the conversion of progesterone and its metabolites into cortisol and aldosterone.

When this enzyme is deficient, the pathways leading to cortisol and aldosterone are blocked. As a result, there is an accumulation of steroid precursors that accumulate upstream of the enzymatic block. In particular, 17-hydroxyprogesterone, which is a direct substrate of the 21-hydroxylase enzyme, cannot be adequately converted to its downstream products. This leads to elevated levels of 17-hydroxyprogesterone and decreased levels of cortisol and aldosterone.

The increase in 17-hydroxyprogesterone is significant and can be detected in newborn screening programs, which aids in the early diagnosis of this condition. The accumulation of this precursor can also lead to the production of androgens, causing virilization and other complications associated with CAH.

In summary, the elevation of 17-hydroxyprog