The role of steroid metabolic profiling as an aid in the diagnosis of familial precocious puberty, a subgroup of true precocious puberty.

We report the results of a study of a rare form of true precocious puberty in a family with a history of the condition. Only the male members manifest the trait, whereas it appears to be carried by both males and females. Routine urinary steroid analysis rapidly eliminated most of the classical enzyme defects associated with premature sexual maturation. Further investigation of urinary steroid extracts using gas chromatography and gas chromatography-mass spectrometry revealed essentially normal prepubertal androgen values for the proband A at 4 years of age, and for his affected and carrier relatives when compared with healthy age-matched individuals. While his plasma gonadotropin levels were in the prepubertal range, his plasma testosterone value was significantly elevated with values just below the normal range for an adult male. This is the fourteenth reported family with a vertical pattern of familial sexual precocity, but the first to have a steroid profile. Analysis suggests sex-limited autosomal dominance with a greater than 90% penetrance. The elevated plasma testosterone concentration, prepubertal plasma gonadotropin concentration, minimal histopathologic evidence of gametogenesis and only moderate increase in testicular volume over the five-year course of follow-up support a diagnosis of the recently described condition of familial gonadotropin independent sexual precocity. The gas chromatography-mass spectrometry urinary profiling shows elevated cortisol output but otherwise normal adrenal function.