Primary testicular abnormalities causing precocious puberty Leydig cell tumor, Leydig cell hyperplasia, and adrenal rest tumor.

The child with testicular enlargement in the absence of gonadotrophin stimulation presents a difficult diagnostic dilemma. Leydig cell tumors, Leydig cell hyperplasia, and tumors of adrenal rest tissue are the primary etiologic considerations. Because of considerable overlap in clinical presentation, careful biochemical and histologic evaluations are necessary to make the diagnosis. These should include serum levels of testosterone, dehydroepiandosterone, androstenedione, 17-hydroxyprogesterone, and 11-desoxycortisol, as well as urinary levels of 17-ketosteroids. If diagnostic changes in the biochemical profile are not present, then testicular biopsy is indicated. Encapsulation, presence or absence of the crystalloids of Reinke, degree of seminiferous tubule maturation, and the site of any abnormal tissue are important observations in the examination of the tissue specimen. Once the diagnosis has been established, then appropriate and specific medical or surgical therapy can be instituted. With appropriate treatment, the long-term prognosis in each condition is good.