[5] The symptoms of Leydig cell hypoplasia include pseudohermaphroditism, i.e., feminized, ambiguous, or relatively mildly underdeveloped (e.g., micropenis, severe hypospadias,[6] and/or cryptorchidism [undescended testes]) external genitalia, a female gender identity or gender variance, hypergonadotropic hypogonadism (hypogonadism despite high levels of gonadotropins), delayed, impaired, or fully absent puberty with an associated reduction in or complete lack of development of secondary sexual characteristics (sexual infantilism), impaired fertility or complete sterility, tall stature (due to delayed epiphyseal closure), eunuchoid skeletal proportions, delayed or absent bone maturation, and osteoporosis.

In the most severe form of the condition in which there is a complete lack of response of the Leydig cells to LH, androgen production by the testicles is virtually negligible and secondary sexual characteristics entirely fail to develop at puberty.

[citation needed] People with Leydig cell hypoplasia type I display no response to the hCG stimulation test; there is no increase in serum levels of testosterone and dihydrotestosterone.

[12] A diagnosis of Leydig cell hypoplasia is usually made in the neonatal period, following the discovery of ambiguous genitalia, or at puberty, when secondary sex characteristics fail to develop.

[11][13] Patients with Leydig cell hypoplasia may be treated with hormone replacement therapy (i.e., with androgens), which will result in normal sexual development and the resolution of most symptoms.