Endocrine Abstracts

Priming with sex steroids prior to stimulation tests for the diagnosis of GH deficiency (GHD) in peripubertal years remains controversial, though some evidence suggests its utility in improving the specificity of GH testing for the distinction between idiopathic GHD (IGHD) and constitutional delay of growth and puberty (CDGP). However, few data are available on the final height (FH) of untreated CDGP patients. In order to better understand the usefulness of priming, we analyzed the FH reached by two groups of consecutive IGHD or CDGP patients.

Study: Forty-five short children (30 males and 15 females; age 8, 9–16 years) underwent sex steroid priming (i.m. testosterone 100 mg; 1–2 mg oral estradiol) before GH stimulation test and were diagnosed with IGHD (25 patients) or CDGP (20 patients) depending on the results of testing. Only IGHD patients were treated with rhGH (0.025–0.035 mg/kg daily). All patients were followed-up until FH.

Results: Mean GH peak following testing was significantly lower in IGHD than in CDGP (P<0.0001). Mean IGF1 SDS was also significantly lower in IGHD (P<0.01): in particular, all children with IGF1 SDS <−2.4 (24% of total) were diagnosed with IGHD. Mean initial height SDS (IHSDS) was similar between the two groups, while target height SDS (THSDS) was significantly lower in IGHD (P<0.05). Both groups of patients reached a FH not statistically different from their TH.

Conclusions: i) Frankly low levels of IGF1 are highly suggestive of GHD, making the use of sex steroid priming unnecessary. ii) The significantly lower THSDS of IGHD patients suggests the contribution of inheritable factors in this category of children. iii) Our data support the usefulness of sex steroid priming in improving the ability of GH stimulation testing to differentiate IGHD from CDGP, thus avoiding an unnecessary expensive treatment.