ESPE Abstracts

Objectives: To investigate the effect of Letrozole on the reproductive function and linear growth in adolescent boys.

Methods: 43 early and middle pubertal boy with seriously damaged predicted adult height(PAH), treated with letrozole 1.5mg/m2/d Po(≯2.5mg/d) with a duration of 3-18 months were enrolled as Short-, medium- and long- treatment group with letrozole of 3-6, 6-12, 12-18 months, respectively. 48 healthy pubertal boys were enrolled as control. Genital stages were evaluated and serum concentrations of FSH, LH, T, E2, IGF-1, AMH and Inhibin B(INHB) were measured at the beginning,mid time and the end of letrozole treatment. Height velocity(HV), HtSDSba, PAH and the serum indexes mentioned above were compared at the beginning and after letrozole treatment.

Results: After letrozole treatment, compared with the control group, mid- and long- treatment group had obviously delayed bone age(BA) and increased PAH. The testicular volume of short- and medium- treatment group were significantly increased compared with the control group, while the long- treatment group had the same increment of testicular volume with the control group. The T levels in the three treatment group were significantly higher than their control group, as well as serum FSH, LH level and LH/FSH. Serum E2 level of long- treament group was significantly reduced than the control group. 17 cases of control group and 13 cases of treatment group had serum AMH, INHB level tested before and after letrozole treatment. Serum AMH level in the control group appeared with a decreasing trend with the progress of puberty, while the treatment group showed the opposite tendency. During the pubertal progress, serum AMH in the control group decreased as blood T elevated, but appeared falling delay in the treatment group. Serum INHB increased after letrozole treament with non-statistically significant less increment in the treatment group compared with the control group. For the linear growth, there was no significant height improvement in short- treatment group, while BA inhibition was evident in long- treatment group. PAH was significantly increased after letrozole treatment in medium- and long- treatment group. IGF1SDS and HOMASDS had no statistical difference before and after treatment.

Conclusion: Letrozole can obviously promote the sex development in adolescent boys, with elevated serum T levels, reduced E2, delayed BA and improved PAH. As to the reproductive function, letrozole may have inhibitory effect on testis maturity and one cannot ignore sertoli cells function affected with letrozole exposure.