Subnormal Serum Insulin-Like Growth Factor-I Levels in Young Adults with Childhood-Onset Nonacquired Growth Hormone (GH) Deficiency Who Recover Normal GH Secretion May Indicate Less Severe but Persistent Pituitary Failure

Abstract

Context: The unexpected observation of a normal GH peak in 22% of young adults with childhood-onset GH deficiency (GHD) and ectopic neurohypophysis has raised questions about the criteria defining GHD in young adults and whether patients with subsequent increases in GH secretion nonetheless have a subtle form of GHD. Objective: Our objective was to determine the characteristics of patients with childhood-onset nonacquired GHD who recover normal peak GH secretion when adult height has been achieved. Design and Setting: We conducted a university hospital-based observational follow-up study. Participants: Sixty-two patients with ectopic neurohypophysis (n = 24), isolated hypoplastic anterior pituitary (n = 14), or normal hypothalamic pituitary area (n = 24) on magnetic resonance imaging (MRI) at the time of GHD diagnosis underwent reevaluation of the GH-IGF-I axis at a mean age of 16.8 ± 1.6 yr. Main Outcome Measures: Outcome measures included clinical and MRI findings and serum IGF-I and peak GH levels. Results: On retesting, peak GH exceeded 10 μg/liter in 31 patients (50%): six (20%) patients with ectopic neurohypophysis, 10 (32%) patients with initially isolated hypoplastic anterior pituitary, and 15 (48%) patients with normal MRI findings. Among these patients, serum IGF-I levels were significantly lower in patients with ectopic neurohypophysis than in those without structural abnormalities of the hypothalamic pituitary axis (n = 25), but patients without structural abnormalities also had significantly lower serum IGF-I levels than control subjects, after controlling for age, sex, and body mass index (mean serum IGF-I levels of 374 ± 83 vs. 446 ± 108 μg/liter; β-coefficient = −72; P = 0.003). Conclusions: The severity of the disease seems to have decreased over time in these patients, who may nonetheless present persistent pituitary failure. The natural history and clinical implications of these findings remain to be clarified. The possibility of a deterioration in the secretion of GH and other pituitary hormones later in life in a subset of these patients warrants the careful long-term follow-up of this population.