Synthesis of Hormones - Testies

Leydig cells and the Sertoli cells are the steroid hormone synthesising cellular sites of the testis. Leydig cells are the major source of these hormones. Testosterone and androstenedione are the main circulating androgens of testicular origin.

                                                                   Figure: (a) Testosterone (b) Andrordenedione

The common metabolites of testosterone are epitestosterone, androstenedione, androstanedione, etiocholanolone, and androsterone. The mechanism of action of androgens is similar to that of the other steroid hormones. Androgens are essential for the control of secondary sex characters of the male and for the functional competence of the accessory reproductive glands and the ducts. The more pronounced metabolic actions of these steroids is the promotion of protein anabolism. Androgens decrease the urinary loss of nitrogen without increasing non-protein nitrogen of the blood, and produce at least a temporary increase in body weight. Since androgens increase protein matrix of bone, they have been used in the clinical treatment of certain skeletal defects., They also promote muscle growth.