17α-Hydroxyprogesterone is a steroid hormone and key intermediate in the biosynthesis of progesterone, cortisol, and other steroids. In medical and laboratory settings, it is primarily used as a diagnostic biomarker for congenital adrenal hyperplasia (CAH), especially due to 21-hydroxylase deficiency, where elevated serum levels help identify the condition. It is also measured to assess adrenal gland function, evaluate endocrine disorders, and monitor hormonal imbalances. As a high-purity reagent, it serves as a reference standard in clinical assays and pharmaceutical research, but it is not typically administered therapeutically (note: the caproate ester form is used for preterm birth prevention).