RESUMO
PURPOSE: Individuals with isolated GH deficiency (IGHD) due to a mutation in the GHRH receptor gene have a normal life expectancy and above 50 years of age, similar total cognitive performance, with better attention and executive function than controls. Our objectives were to evaluate their brain morphometry and brain aging using MRI. METHODS: Thirteen IGHD and 14 controls matched by age, sex, and education, were enrolled. Quantitative volumetric data and cortical thickness were obtained by automatic segmentation using Freesurfer software. The volume of each brain region was normalized by the intracranial volume. The difference between the predicted brain age estimated by MRI using a trained neuronal network, and the chronological age, was obtained. p < 0.005 was considered significant and 0.005 < p < 0.05 as a suggestive evidence of difference. RESULTS: In IGHD, most absolute values of cortical thickness and regional brain volumes were similar to controls, but normalized volumes were greater in the white matter in the frontal pole and in the insula bilaterally, and in the gray matter, in the right insula and in left Caudate (p < 0.005 for all comparisons) We also noticed suggestive evidence of a larger volume in IGHD in left thalamus (p = 0.006), right thalamus (p = 0.025), right caudate (p = 0.046) and right putamen (p = 0.013). Predicted brain ages were similar between groups. CONCLUSION: IGHD is primarily associated with similar absolute brain measurements, and a set of larger normalized volumes, and does not appear to alter the process of brain aging.
RESUMO
OBJECTIVE: Somatotrophs represent the majority of cells in the anterior pituitary, and their numeric reduction can cause anterior pituitary hypoplasia (APH). Small numbers of patients with familial isolated GH deficiency (IGHD) due to bi-allelic mutations in the GHRH receptor (GHRHR) gene (GHRHR) have been reported to have APH. We tested if APH was present in a large cohort of patients homozygous and heterozygous for a GHRHR mutation. DESIGN: We studied pituitary morphology in adult and pediatric age subjects (8 years of age and older) belonging to a large extended Brazilian kindred with a high prevalence of IGHD due to a null GHRHR mutation. METHODS: We performed brain magnetic resonance imaging (MRI) in 38 subjects, divided into four groups: group I: normal adults (five males, four females, age 38+/-11.7 years); group II: heterozygous adults (six males, seven females, age 42.23+/-8.8 years); group III: homozygous GH-naive affected adults (three males, five females, age 41.4+/-15.0 years); group IV: homozygous affected children (three males, five females, age 11.9+/-2.5 years). Results are expressed as means+/-s.d. RESULTS: Pituitary height (mm) was not different between groups II and I (4.61+/-1.55 and 4.41+/-0.62 respectively), but it was significantly reduced in groups III (2.67+/-0.87, P<0.001) and IV (2.87+/-0.79, P<0.001) compared with group I. Pituitary volume (mm(3)) was normal in group II (417.12+/-140.86), but it was significantly reduced in groups III and IV (124.06+/-64.27 and 155.68+/-39.79 respectively vs 414.56+/-71.57; both P<0.001). The volume ratio (calculated by multiplying the pituitary volume by 1000 and dividing it by cranial volume) was significantly lower in the affected subjects (groups III and IV) (0.06+/-0.02) than in unaffected (groups I and II) (0.15+/-0.04; P<0.0001), demonstrating that APH is not due to reduction of cranial volume. CONCLUSIONS: APH is present from childhood in patients homozygous for an inactivating GHRHR mutation, but it does not occur in heterozygous subjects. In our cohort, the presence of normal anterior pituitary size by MRI rules out homozygosity for a GHRHR mutation in subjects who are 8 years of age or older.
