Endocrine Abstracts

The most appropriate way to manage growth hormone replacement (GH) in the transition to adulthood in children treated with GH for GH deficiency (GHD) is controversial. The GH Research Society suggest that retesting of GH status at final height (FH) is unnecessary in the presence of 'severe organic GHD' and cranial irradiation falls into this etiological category. This recommendation has never been validated.

To investigate whether patients diagnosed in childhood as GHD secondary to irradiation require retesting after FH, GH status has been reassessed in a large cohort of irradiated children treated with GH during childhood.

73 children underwent biochemical assessment of GH status after irradiation and again at FH after GH had been discontinued; 67 of the 73 patients underwent two provocative tests at each time point. The characteristics of the cohort are:-median (range) age at irradiation 5(1-11)y; median biological effective dose (BED) of irradiation to the HP axis 54(23-82)Gy.

During childhood patients with peak GH<20mU/L to provocative testing are treated with GH whereas in adulthood only those with severe GHD, peak GH<9mU/L, are considered. GH status in childhood has been grouped as follows:- peak GH<9mU/L to both tests ie severe GHD (group 1); one test with a peak GH<9mU/L and the other >9mU/L or peak GH of 9-20mU/L to both tests ie moderate GHD (group 2). In childhood 33 & 39 patients were in group 1 & 2 respectively. At retesting severe GHD was diagnosed in 64%(21/33) and 44%(17/39) of those diagnosed in childhood as group 1 & 2. In total 48%(35/73) of the cohort did not fulfill the severe GHD biochemical criteria for GH replacement in adulthood. Using multiple linear regression, GH status at retesting is predicted by BED, age at irradiation and use of chemotherapy.

In conclusion the diagnosis of radiation induced GHD in childhood should not be taken as irrefutable evidence of permanent 'severe organic GHD' and our recommendation is that retesting of GH status at FH is mandatory.