Activating mutations in the luteinizing hormone receptor gene: a human model of non-follicle-stimulating hormone-dependent inhibin production and germ cell maturation.
BACKGROUND
Familial male-limited precocious puberty is a dominant autosomal genetic disease caused by activating LH receptor gene mutations, clinically expressed only in males. In preliminary studies, in addition to the expected testosterone increase, we found high inhibin B levels before the age of normal puberty.


OBJECTIVE
The objective of the study was to assess the cellular origin of serum inhibin thanks to testis section immunostaining.


METHODS
Serum testosterone, gonadotropin, inhibin B, pan-alphaC-inhibin, and anti-Mullerian hormone levels were measured. Immunostaining was performed using specific anti-alpha- and anti-beta-subunit antibodies.


METHODS
Five boys from three families (mutation M398T or I542L) were investigated at onset (2-6 yr), on ketoconazole treatment, and at adolescence. Testis biopsies were performed in three subjects before the disease was fully characterized.


RESULTS
The high testosterone levels were suppressed by ketoconazole. Anti-Mullerian hormone levels were inversely related to testosterone: low at diagnosis, elevated after testosterone suppression. Despite FSH suppression, inhibin B and pan-alphaC-inhibin levels were high from clinical onset to adolescence. Biopsy specimens showed normal Sertoli cell complement and germ cell maturation until the spermatocyte II stage. Sertoli and Leydig cells displayed positive inhibin alpha-subunit immunostaining. Only Leydig cells and spermatogonia stained positively for the inhibin betaB-subunit.


CONCLUSIONS
Familial male-limited precocious puberty is a unique model of inhibin B secretion, demonstrating that Leydig cells can produce significant amounts of the dimeric molecule. Our results also suggest that the pubertal FSH rise is not required for full expression of the two inhibin B genes and for the initiation of germ cell maturation.
Soriano-Guillen
Leandro
L
Department of Pediatric Endocrinology, Centre Hospitalier Universitaire Cochin Saint Vincent de Paul, 82 avenue Denfert-Rochereau, 75014 Paris, France.
Mitchell
Valerie
V
Carel
Jean-Claude
JC
Barbet
Patrick
P
Roger
Marc
M
Lahlou
Najiba
N