Commonly known for testosterone secretion, the testes also produce the protein hormones anti-müllerian hormone (AMH), inhibin B, and insulin-like factor 3 (INSL3). AMH and inhibin B are secreted by Sertoli cells, whereas INSL3 is a Leydig cell product. AMH is involved in fetal sex differentiation and induces the regression of the anlagen of the uterus and fallopian tubes. INSL3 participates in fetal testicular descent. Serum testicular protein hormone assessment can be very useful and complementary to testosterone measurements in patients with DSD. AMH and inhibin B determination is extremely helpful during childhood, when basal testosterone is normally low. Serum AMH and inhibin B above the female range are indicative of the presence of testicular tissue, and their circulating levels reflect the amount of functional Sertoli cells. In DSD patients with normal male levels of AMH and inhibin B, the diagnosis of gonadal dysgenesis can be ruled out, and isolated androgen secretion deficiency or androgen insensitivity should be suspected. In externally virilized XY patients with persistent müllerian ducts, serum AMH levels determine the diagnosis to AMH deficiency or resistance. At pubertal age, inhibin B levels serve to predict spermatogenic development.