Breast enlargement in the prepubertal male patient without accompanying endocrine abnormality is rare. Whether prolactin is involved in the development of idiopathic prepubertal gynecomastia is at present unknown. Serum prolactin levels were not detectably elevated in adult patients with gynecomastia.1,2 However, prolactin levels have not yet been reported in patients with prepubertal gynecomastia. The following is a case report of a prepubertal boy with gynecomastia, including serum prolactin levels as well as other endocrine parameters used to evaluate patients with this condition.
Materials and Methods.—Plasma testosterone, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels were measured by radioimmunoassay.3, 4 Serum prolactin was determined by a double antibody homologous radioimmunoassay using a lactoperoxidose method of iodination.5 The mean serum prolactin level of 14 normal preadolescent boys (age 0 to 9 years) was 12.0 (±7.6 SD) ng/ml (unpublished data). Urinary 17 hydroxy and 17 ketosteroids were measured using