A 21 year old female presents with oligomenorrhea. On examination she has excess facial hair growth, and lab investigation showed an increase in free serum testosterone levels. USG abdomen done shows normal ovaries. What is the most probable diagnosis?

All the 4 options given above can cause hirsutism in this age group. Since the USG abdomen shows normal ovaries, PCOD and testosterone secreting tumours are ruled out. In idiopathic hirsutism, there is only a mild increase in facial hair and will have normal menstrual cycles. In this condition, levels of free serum testosterone levels are elevated but have normal total serum testosterone levels. So, this patient is most likely suffering from late onset congenital adrenal hyperplasia. Late onset congenital adrenal hyperplasia: It is a heterogenous group of mild disorder of coisol biosynthesis and is an impoant cause of adult onset hirsuitism. It is mostly caused by deficiency of 21 alpha hydroxylase which leads to increased production of 17 hydroxyprogesterone and androstenedione with resultant hyperandrogenicity. These patients are not coisol deficient due to increased ACTH secretion.