ketosteroid

Ketosteroid is a steroid molecule that contains a ketone functional group (C=O). In common usage, the term usually refers to steroids with a carbonyl at the C-3 position, known as 3-ketosteroids, but it also encompasses steroids with carbonyls at other positions, particularly the C-17 position (17-ketosteroids).

Structure and chemistry: Ketosteroids share the tetracyclic cyclopentanoperhydrophenanthrene nucleus typical of steroids. The introduction of a ketone increases polarity and alters chemical reactivity and receptor interactions. The most common site is the 3-position; additional ketone groups give di- or poly-ketosteroids such as 3,17-dione.

Biosynthesis and metabolism: Ketosteroids arise by oxidation of hydroxy groups during steroidogenesis or catabolic pathways. They serve as intermediates in the production of active hormones and can be further reduced or conjugated for excretion. In humans, many ketosteroids are excreted in urine as metabolites of androgens and estrogens; the pool of 17-ketosteroids has been used in clinical assays.

Clinical and analytical use: Historically, urinary 17-ketosteroid tests were used to assess androgen production, often in diagnosing endocrine disorders; now more comprehensive steroid profiling by mass spectrometry is common. Ketosteroids are also important in pharmaceutical chemistry as intermediates in the synthesis of corticosteroids and other steroid drugs.

Examples: 3-ketosteroids include progesterone, testosterone, and androstenedione, which bear a carbonyl at C-3; 17-ketosteroids include DHEA and androsterone, which carry a ketone at C-17.