Serum Ghrelin Concentrations are Increased in Children with Growth Hormone Insensitivity and Decrease during Long-Term Insulinlike Growth Factor-I Treatment

Abstract

Background

Ghrelin increases food intake, body weight, and growth hormone (GH) secretion. Serum concentrations of ghrelin are low in obese hyperinsulinemic persons, are reduced by infusion of insulin into normal-weight subjects, and are increased in underweight hypoinsulinemic patients with anorexia nervosa. Laron syndrome is an autosomal recessive disorder of GH insensitivity that results in decreased insulinlike growth factor-I (IGF-I) synthesis and growth failure. These patients have elevated GH levels, excess adipose tissue, and are insulin resistant. Because IGF-I has insulinlike actions and patients with GH insensitivity syndrome (GHIS) exhibit excess adiposity, we sought to determine whether ghrelin levels were elevated in these patients and potentially regulated by IGF-I replacement.

Methods

Thirteen children with GHIS and 20 normal control children matched for age, sex, and body mass index underwent complete physical examination and a fasting blood draw at baseline. The GHIS subjects then underwent follow-up fasting blood draws during therapy with human recombinant IGF-I (80-120 μg/kg, given subcutaneously twice daily). Fasting glucose, insulin, and IGF-I concentrations were measured at the time of collection. Fasting total ghrelin levels were measured on stored serum samples.

Results

The GHIS subjects had 2-fold higher fasting ghrelin levels (2926 ± 1869 pg/mL) compared with the normal control children (1492 ± 493 pg/mL; P = 0.009), and mean ghrelin values were reduced 56% during 6.4 ± 0.2 years of IGF-I replacement (P < 0.05).

Conclusions

Growth hormone resistance and low IGF-I levels are associated with elevated ghrelin levels, which may potentiate GH secretion and adiposity in these children. Suppression of ghrelin during IGF-I treatment suggests a novel mechanism potentially regulating ghrelin levels.