This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Disorders in Menstruation, Subject name: Gynaecology & Obstetrics
A 15-year-old girl c/o failure to attain menarche. Her height is 4 feet. She has not yet developed secondary sexual characteristics. If USG shows uterus and vagina. FSH and LH levels are high. What is the best step in confirming the diagnosis? 
Select and explain. 
A. Perform a CT, B. Perform a Karyotype, C. Perform a buccal smear, D. Perform progesterone withdrawal test
B: Perform a Karyotype
Answer: B: Perform a Karyotype 
Explanation: Ans. is b, i.e. Perform a karyotype1st step in primary amenorrhea is to identify the site of lesion by doing Hormonal profileIn question : LH and FSH are highUSG: shows uterus and vagina are presentPt has short height (4 feet)No secondary sexual characteristicsNow since LH and FSH are high and estrogen is low (as secondary sexual characteristics are absent)[?] It is a case of hypergonadotropic hypogonadism --so most probably it is Turners syndrome. This can be confirmed by doing karyotyping.Always remember in Primary amenorrhea1st Test: Hormonal ProfileBest Test: Karyotyping