Prevalence of Congenital Adrenal Hyperplasia in South Indian Polycystic Ovarian Syndrome Women.

Introduction: Polycystic ovary syndrome (PCOS) is a prevalent endocrine disorder characterised by hyperandrogenism and ovulatory dysfunction. Nonclassic congenital adrenal hyperplasia (NCCAH) is an important differential diagnosis, but its prevalence in Indian women remains unclear. Previous North Indian studies reported variable rates using less specific assays. This study aimed to determine the prevalence and clinical characteristics of NCCAH among hyperandrogenemic South Indian women with PCOS. Methods: This cross-sectional study was conducted at a tertiary care centre in South India (January 2019 to December 2022). Women aged ≥18 years meeting Androgen Excess Society criteria for PCOS were included. Hyperandrogenemia was defined as serum total testosterone >0.55 ng/ml by chemiluminescent immunoassay. All participants underwent serum steroid profiling 60 minutes after Acton Prolongatum-stimulation using liquid chromatography-tandem mass spectrometry. The serum steroid levels of women with PCOS were compared with those of healthy volunteers. Results: Of 182 screened women, 128 were diagnosed with PCOS. Acton Prolongatum-stimulated steroid profiling was performed in 120 women. Three (2.5%) were diagnosed with congenital adrenal hyperplasia (CAH)-two with classic 21α-hydroxylase deficiency (21OHD) and one with 11β-hydroxylase deficiency. All three showed severe hirsutism, clitoromegaly and severe hyperandrogenemia (>1.5 ng/ml). None were diagnosed with nonclassic 21OHD. Compared with controls, PCOS women had significantly higher testosterone and androstenedione levels with no significant difference in other steroid levels. Conclusions: NCCAH is rare among South Indian women with PCOS, whereas the simple virilising form of classic CAH may often mimic PCOS. Severe hyperandrogenism distinguishes CAH from PCOS and helps prioritise them for CAH screening.