**Question:** A 16 years old female with normal pubic hairs and breast presented with primary amenorrhea. On examination, there was blind vagina and absent uterus. Diagnosis is:

A. Turner's syndrome
B. Congenital adrenal insufficiency
C. Hypothyroidism
D. Congenital adrenal hyperplasia

**Correct Answer:** A. Turner's syndrome

**Core Concept:** Primary amenorrhea is defined as the absence of menarche in a girl by the age of 16 years. In Turner's syndrome, a woman has two X chromosomes but one of them is partially or completely missing, leading to a range of clinical features.

**Why the Correct Answer is Right:** Turner's syndrome is related to primary amenorrhea because it is a genetic disorder that results in the partial or complete absence of one of the two X chromosomes. In such cases, girls may have delayed or absent puberty, breast development, and menarche. The absence of a uterus and a blind vagina in this patient supports the diagnosis of Turner's syndrome. Turner's syndrome is characterized by short stature, webbed neck, low-set ears, broad chest with webbing between the clavicles, and cardiovascular, renal, and skeletal abnormalities.

**Why Each Wrong Option is Incorrect:**

**A. Congenital adrenal insufficiency (CAI):**
This option refers to a disorder in which the adrenal glands are not producing sufficient amounts of steroid hormones. CAI is not related to amenorrhea in females, as it primarily affects adrenal hormones, not sex hormones.

**B. Congenital adrenal hyperplasia (CAH):**
Similar to congenital adrenal insufficiency, congenital adrenal hyperplasia is a disorder affecting the adrenal glands, primarily affecting cortisol production. It is not directly related to amenorrhea in females.

**C. Hypothyroidism:**
Hypothyroidism is a disorder of thyroid hormones, which are not directly involved in the development of amenorrhea in females.

**D. Congenital adrenal hyperplasia (CAH):**
This option is similar to congenital adrenal insufficiency and hypothyroidism, both of which affect hormones produced by the glands mentioned, not directly related to amenorrhea in females.

**Core Concept:** Hypothalamic-pituitary-ovarian axis is responsible for the development of secondary sexual characteristics and menstruation in females. Turner's syndrome interferes with the development of the hypothalamic-pituitary-ovarian axis, leading to the absence of menstruation (amenorrhea) and secondary sexual characteristics. In Turner's syndrome, there is a deficiency of sex steroids, specifically estrogen and progesterone, leading to the absence of menstruation and secondary sexual characteristics like breast development and the absence of pubic hair.

**Why Turner's Syndrome is the correct answer:**
Turner's syndrome is a genetic disorder characterized by the absence of one X chromosome in