Older Individuals Heterozygous for a Growth Hormone-releasing Hormone Receptor Gene Mutation Are Shorter Than Normal Subjects

Growth hormone (GH)-releasing hormone (GHRH) is the most important stimulus for GH secretion by the pituitary gland. Subjects homozygous for GHRH receptor (GHRHR) gene (GHRHR) inactivating mutations have severe GH deficiency, resulting in severe short stature if not treated. We previously reported that young adults heterozygous for the c.57+1G>A null GHRHR mutation (MUT/N) have reduced weight and body mass index (BMI) but normal stature. Here we have studied whether older MUT/N have an additional phenotype. In a cross-sectional study, we measured height, weight and blood pressure, and calculated BMI in two groups (young, 20-40 years of age) and old (60-80 years) of individuals heterozygous for the same GHRHR mutation, and compared with a large number of individuals of normal genotype residing in the same geographical area. Standard deviation score (SDS) of weight was lower, and BMI had a trend toward reduction in young heterozygous compared with young normals, without significant difference in stature. Conversely, SDS of height was lower in older heterozygous individuals than in controls, corresponding to a reduction of 4.2 cm. These data show a reduced stature in older subjects heterozygous for the c.57+1G>A GHRHR mutation, indicating different effects of heterozygosis through lifespan.