**Question:** In a child with ambiguous genitalia, the first test to be done is:

A. Karyotyping
B. Hormonal stimulation test
C. Ultrasonography
D. Measurement of الغدد التناسلية-specific hormones (LH and FSH)

**Core Concept:**
Ambiguous genitalia refers to a condition in which the external genitalia of an infant do not clearly indicate male or female. This can be due to genetic factors, hormonal imbalances, or other developmental abnormalities. The appropriate initial tests aim to determine the underlying cause, guide further management, and predict the sex of the fetus or chromosomal diagnosis.

**Why the Correct Answer is Right:**
The correct answer is D: Measurement of gonadotropin-specific hormones (LH and FSH) because these hormones are essential for the development of male and female external genitalia during fetal life. Elevated levels of LH and FSH indicate a hormonal imbalance, while normal levels suggest that the ambiguous genitalia is due to genetic factors or other developmental abnormalities.

**Why Each Wrong Option is Incorrect:**
A. Karyotyping (Option A) is a genetic test that provides information about the number and types of chromosomes. While karyotyping can provide valuable information, measuring gonadotropin levels (Option D) is more directly related to the cause of ambiguous genitalia, as hormonal imbalances are a common cause.

B. Hormonal stimulation test (Option B) may be performed later to evaluate the response to exogenous gonadotropin administration. However, measuring gonadotropin levels is a more direct approach to understanding the cause of ambiguous genitalia.

C. Ultrasonography (Option C) is a valuable imaging modality used for evaluating genitalia, but measuring gonadotropin levels provides a more direct indication of the hormonal status and is crucial in determining the cause of ambiguous genitalia.

**Clinical Pearl:**
Measuring gonadotropin levels (LH and FSH) is an essential initial step in assessing ambiguous genitalia in children. It helps differentiate genetic causes (Klinefelter syndrome, Turner syndrome, etc.) from hormonal causes (hypogonadotropic hypogonadism, ambiguous genitalia, etc.). Understanding the hormonal status can guide further diagnostic workup, treatment, and prognosis.