Male sex hormone. Polarised light micrograph of crystals of Androstenedione (4-Androstene-3,17- dione). This is a naturally-occurring androgen, the class of hormones associated with the development of male reproductive organs and secondary sex characteristics. Androstenedione is part of the biosynthesis pathway in the production of testosterone. Magnification: x8 at 35mm size, x16 at 6x7mm size.