Androgen production in adrenocortical H295R cells is regulated by thyroid hormone T3 without reciprocal thyroid axis modulation in pediatric CAH.

Thyroid hormones (THs) are critical regulators of human development, cellular differentiation, and metabolism. While their systemic effects are well established, their role in adrenal androgen production remains poorly defined. Moreover, potential feedback regulation of the hypothalamic-pituitary-thyroid (HPT) axis by adrenal androgens has not been thoroughly investigated. This study aimed to clarify the regulatory effects of THs on adrenal androgens and to investigate potential feedback mechanisms in patients with congenital adrenal hyperplasia (CAH). In an in-vitro experiment, treatment with 3,3',5-triiodo-L-thyronine (T3) on adrenocortical carcinoma H295R cells significantly reduced dehydroepiandrosterone (DHEA) and DHEA-sulfate production while modestly increasing testosterone (T) and androstenedione (A4). These changes were associated with an increase in expression of HSD3B2 and AKR1C3, and a decrease of CYP17A1. Transcriptomic analysis additionally revealed enrichment of pathways related to steroidogenesis and adrenal development through T3 treatment. In the clinical part of the study, hormone levels in pediatric CAH patients were analyzed. Serum free thyroxine (fT4) and thyroid-stimulating hormone (TSH) showed weak negative correlations with the adrenal androgens DHEA and A4. However, no differences in fT4 or TSH concentrations were observed between well-controlled and hyperandrogenic patients, suggesting a lack of feedback regulation by adrenal androgens on the HPT axis. In conclusion, these findings suggest that THs regulate adrenal androgen production by modulating the activity of key steroidogenic enzymes. This relationship appears to be predominantly unidirectional, with THs influencing adrenal steroidogenesis but adrenal androgens not altering HPT axis function.