**Question:** 17-OH progesterone level in congenital adrenal hyperplasia in a 1-year-old child (in ng/dl)

**Core Concept:**
Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive genetic disorders affecting the adrenal glands. In these conditions, the adrenal glands produce increased amounts of androgens and cortisol due to deficient action of specific enzymes involved in cortisol and aldosterone biosynthesis. 17-hydroxyprogesterone (17-OHP) is a hormone that can be measured to diagnose and monitor CAH.

**Why the Correct Answer is Right:**
In a 1-year-old child with suspected CAH, a raised 17-OHP level indicates impaired 21-hydroxylase enzyme function, as this enzyme is involved in cortisol biosynthesis and is deficient in CAH. A level of 17-OHP greater than 10 ng/dL is considered diagnostic for CAH. In this case, the correct answer is **D**, as the 17-OHP level in a 1-year-old child with CAH would typically be elevated.

**Why Each Wrong Option is Incorrect:**

A. 17-OHP level is expected to be normal in a healthy 1-year-old child and can be influenced by various factors, making it unreliable as a diagnostic marker.

B. Although a raised 17-OHP level indicates CAH, the levels can be influenced by factors such as stress, illness, or medications, making it unreliable as a definitive diagnostic tool.

C. A decreased level of 17-OHP is expected in a 1-year-old child with CAH, contradicting the typical finding of elevated levels in this condition.

**Clinical Pearl:**
The diagnosis of CAH in a 1-year-old child is based on a combination of clinical features, genetic testing, and hormonal profiles, including elevated 17-OHP levels. A single elevated 17-OHP level may not be definitive in making the diagnosis, as other factors can affect the hormone levels. Confirmation is usually achieved through genetic testing and clinical correlation, including the typical clinical features of CAH.