Female sex hormone. Polarised light micrograph of crystals of 17- alpha-hydroxyprogesterone, also known as 17aOHP. It is one of the naturally- occurring progestagens, the class of hormones associated with the preparation of the body for pregnancy. A synthetic form may be used to prevent miscarriage and to treat menstrual disorders. 17aOHP is secreted in the ovaries, where it is synthesised by the action of enzymes on pregnenolone. It may be further processed by the body to produce androgens, estrogens or corticosteroids. Magnification x8 at 35mm size.