Endocrine Abstracts

Aromatase inhibitors (AIs) have been proposed as a modality in the treatment of short stature in boys. Improvement in final height and predicted final height has been observed in children with constitutional delay of growth and puberty and idiopathic short stature. AIs block the conversion of androgens to estrogens and thus may delay epiphyseal fusion and thereby prolong linear growth. We report our experience with the use of letrozole, a third generation AI, in a boy with genetic short stature and advanced bone age (BA).

Case report: An 11.8 years old boy was referred because of short stature and advanced BA. Height SDS of his mother and father were −1.87 and −1.6 respectively. His height SDS was −1.52. BA (TW2) was advanced by 3 years. Investigations for late onset congenital adrenal hyperplasia and skeletal dysplasia were negative. Predicted final height was 158.1 cm (−2.69 SDS). Letrozole was started at 12.6 years and GnRH analogue was introduced at the onset of puberty. When growth velocity declined once puberty halted, GH treatment was also added. Puberty progressed normally when the GnRH analogue was stopped at 13.6 years. Serial estimations of BA (TW2) showed arrest of further progression. At 16.0 years, the BA was delayed by 0.7 years. During 3.4 years of treatment BA advanced only 0.5 years. The predicted final height increased by 8 to 166.1 cm (−1.54 SDS). Elevated gonadotrophins (FSH 12.3 U/l, LH 7.5 U/l) and testosterone (45.6 nmol/l) was observed. This was probably the result of interference to the negative feedback mechanism from lack of estrogen. No adverse effects were noticed during this treatment trial.

Conclusion: AIs may be useful for enhancing final height in boys with short stature and advanced BA. This case illustrates that letrozole is effective even when commenced at a relatively late phase of skeletal growth and despite the presence of an advanced BA.