Luteinizing hormone regulation by sex steroids in men with germinal and Leydig cell tumours.

OBJECTIVE: We examined the gonadotrophin secretion in patients with increased plasma concentrations of testosterone and oestradiol due to hCG-producing tumours.

DESIGN: Comparison of plasma gonadotrophin concentrations before and after stimulation by GnRH, in eight men with hCG-producing tumours resulting in increased testosterone and oestradiol plasma levels, and in 29 men with Leydig cell tumours resulting in increased oestradiol and normal to low testosterone plasma levels.

PATIENTS: Eight men with hCG-producing tumours (six with testicular tumours, two with extratesticular tumours), 29 men with Leydig cell tumours and 15 normal men. The six men with germinal cell tumours of the testis were studied before and after unilateral orchidectomy.

MEASUREMENTS: Plasma concentrations of hCG, testosterone and oestradiol were measured before and after intramuscular injection of hCG. LH and FSH were measured before and after intravenous injection of 100 micrograms GnRH.

RESULTS: Plasma LH and FSH concentrations were low in patients with germ cell tumours, who exhibited increased plasma testosterone and oestradiol concentrations, and were normal in patients with Leydig cell tumours, in whom oestradiol only was increased. Plasma LH and FSH were normalized in the five patients with successful (e.g. normal hCG, testosterone and oestradiol) unilateral orchidectomy. Basal plasma testosterone concentrations correlated positively (P < 0.01) with plasma oestradiol concentrations in patients with germ cell tumours and negatively (P < 0.01) in patients with Leydig cell tumours.

CONCLUSIONS: In patients with hCG-secreting germ cell tumours complete suppression of plasma LH and FSH with increased plasma concentrations of both testosterone and oestradiol are often discovered. No such gonadotrophin suppression is found in patients with Leydig cell tumours, but the negative correlation observed between plasma testosterone and oestradiol in these patients suggests a weak negative feedback effect of oestradiol on LH secretion, which cannot be demonstrated by basal LH measurements in plasma.