ESPE Abstracts

Background: It has been reported that 25–75% of patients with diagnosis of growth hormone deficiency (GHD) may show normal growth hormone (GH) responses in repeated stimulation tests after completion of treatment. Retests are typically conducted following completion of growth phase. In a small number of studies retests are conducted during early stages of GH therapy. Accuracy of early retesting to exclude GHD can be evaluated by adult heights of those whose GH treatment were ceased after a normal GH response at retest. This study's objective is to evaluate how accurately early retesting can exclude GHD.

Methods: 185 patients (77girls) who were treated with GH for a diagnosis of isolated GHD, and retested after first year of treatment were included in the study. Retesting of 75 patients (34girls) revealed a peak GH level ≥10ng/ml, and GH treatment was discontinued in these patients, it was continued in those with a peak response <10ng/ml. All patients were followed until final height. Chronological age, bone age, height-SDS, IGF1 and IGFBP3 levels, serum peak GH level and target height-SDS of all patients, both at beginning of GH treatment, and at retesting were acquired retrospectively from hospital records. Patients were divided into two groups according to peak GH response at retesting (GH<10ng/ml vs GH≥10ng/ml). Adult heights of all patients were recorded.

Results: At diagnosis, means of chronological and bone age, and height-SDS of patients with peak GH<10ng/ml at retesting were lower than those with peak GH≥10ng/ml; while means of IGF1 and IGFBP3-SDS were similar in these groups. GH response was normal (≥10ng/ml) at retesting in 18% of patients with peak GH<5ng/ml at diagnosis, and in 51.6% of patients with peak GH at 5-10ng/ml at diagnosis (P<0.001). Those with a peak GH<10ng/ml at retesting had an increased growth velocity during first year of GH treatment than those with a normal GH response at retesting. On the other hand, growth rates between those continuing and discontinuing GH after retest were not different. Adult height-SDS, height gains and target heights were all similar in both groups.

Conclusion: Patients with isolated GHD, whose GH treatment was discontinued after a normal GH response at early retesting (1st year of treatment), reached adult heights comparable to their target heights as well as to adult heights of those whose treatment was continued. Considering problems in diagnostic accuracy of GH stimulation tests, early retesting may prevent unnecessary treatment in some cases initially diagnosed as isolated GHD who proved to be normal during retesting.