A pilot study of growth hormone administration in boys with predicted adult short stature and near-ending growth

• A mean 72.5 ± 9 μg dose of rhGH/k.d was given for 11 ± 4.8 months to boys aged 15.5 ± 1 years.
• Adult height reached -1.8 ± 0.9 SDS, while predicted height was -2.9 ± 0.6 SDS (P = 4.10− 4).
• A short period of rhGH administration may increase adult height significantly in boys with near-ending growth.
• Knee score (R = -0.84, P = 8 x 10− 4) and growth velocity at rhGH onset (R = 0.79, P = 5 x 10− 4) were predictors of the height increment, but not bone age.

ContextThe growth-promoting effect of starting recombinant human growth hormone (rhGH) at the time of near-ending growth has not been studied in sexually mature boys who will have idiopathic short stature (ISS) as adults because it is believed that such an advanced stage of puberty would preclude favorable results.Objectives1) To explore the effects of starting rhGH administration at time of near-ending growth in boys with ISS. 2) To search for predictors of response to rhGH.SubjectsFifteen boys aged 15.5 ± 1 years terminating puberty were growing at a rate < 2 cm/6 months towards a predicted adult height (PAH) < − 2.5 SDS.MethodsParticipants received 0.50 ± 0.06 mg/kg·wk of rhGH according to a target-to-treat protocol. When growth became less than 0.5 cm in 3 months or when height has reached 169 cm, rhGH was ceased. Testosterone, growth velocity (GV), height, serum IGF-1, bone age (BA) at hand–wrist and knee score were measured at onset; IGF-1 and height were monitored every 3 months. A formula for PAH was developed. Height increment (HI, adult height-starting height) and height gain (HG, adult height-PAH) were calculated.ResultsFollowing rhGH administration for 11.1 ± 4.8 months, GV-SDS increased from − 2.5 ± 1.7 to 3.5 ± 4.3 (P = 2 × 10− 4), HI = 8.5 ± 3.7 cm, HG = 6.8 ± 4.8 cm and adult height was − 1.8 ± 0.9 SDS, compared to a PAH of − 2.9 ± 0.6 SDS (P = 4 × 10− 4). Knee score (P = 2 × 10− 3), GV at rhGH onset (P = 8 × 10− 3) and rhGH dose (P = 8 × 10− 3) were identified as predictors of HI and HG, but BA was not.ConclusionsOur study suggests that 1) a short period of rhGH administration can increase true adult height significantly in boys with ISS at time of near-ending growth; and 2) knee score rather than BA should be used to identify rhGH responders. These preliminary observations await confirmation by larger randomized trials.