Endocrine Abstracts

Introduction: GH neurosecretory dysfunction (NSD) refers to children with abnormal auxology, normal GH responses to provocative testing, but with impaired spontaneous GH secretion over 24 h, leading to low IGF1 concentrations. It is thought to be due to abnormal hypothalamic function with aberrant GHRH and somatostatin secretion leading to impaired GH secretion and subsequently suboptimal growth.

Methods: We reviewed children admitted for spontaneous GH secretory profiles over the last 4 years. We aimed to identify children with growth failure who achieved adequate GH concentrations following stimulation but showed evidence of NSD on an overnight GH profile. We evaluated growth velocity and IGF1 before and after commencing GH treatment. All children diagnosed with NSD were further investigated using neuroimaging (MRI brain/pituitary).

Results: We identified four children with short stature (height <−2.5 SDS) and sub-optimal growth velocity who demonstrated inadequate endogenous GH secretion. These children had no or only one GH peak >7 μg/l over 12 h. All children had previously passed a standard GH stimulation test with stimulated GH concentrations ranging from 10.2 to 21.1 μg/l. However IGF1 concentrations were below −2 SDS in all children. All four children had structural abnormalities of the hypothalamic–pituitary axis including septo-optic dysplasia, anterior pituitary hypoplasia, ectopic posterior pituitary and abnormalities of the infundibulum. Two children subsequently developed multiple pituitary hormone deficiency. All children were commenced on GH treatment and showed normalisation of growth velocity and IGF1 concentrations.

Conclusions: Structural abnormalities of the hypothalamic–pituitary axis may be associated with NSD of GH secretion. Children with significantly abnormal auxology may therefore warrant further investigation in the form of neuroimaging and overnight GH profiling even if they achieve a normal GH peak following provocation. Children with GH deficiency secondary to NSD clearly benefit from treatment despite not being NICE approved; this may soon require discussion with commissioning groups.