Context: Patients with GHRH receptor (GHRH-R) mutations present with familial isolated GH deficiency, which untreated leads to a severely compromised adult height. Few data are available about the efficacy of treatment with GH in combination with a gonadotropin-releasing hormone (GnRH) analog (GnRHa) in adolescence.

Objective: To describe the evolution of growth and skeletal age of a brother and sister of Moroccan descent with a homozygous GHRH-R mutation who presented at an advanced age (16 and 14.9 yr, respectively) and pubertal stage (Tanner stage G4 and B3, respectively) with a height of -5.1 SDS and -7.3 SDS on treatment with a combination of GH and GnRHa for 2.5 and 3 yr followed by GH alone.

Methods: GH was given in a dosage of 0.7 mg/m²/d (25 µg/kg/d) sc and triptorelin in a dosage of 3.75 mg/4 wk im. Height and pubertal stage were measured three-monthly, bone age yearly.

Results: Combined GH and GnRHa treatment resulted in a height gain of 24 and 28.2 cm, respectively, compared to the initial predicted adult height by the method of Bayley-Pinneau. Adult height was within the population range and well within the target range.

Conclusions: Our patients demonstrate that, in case of isolated GH deficiency caused by a GHRH-R mutation, combined treatment of GH and GnRHa can be very effective in increasing final height, even at an advanced bone age and pubertal stage.