Context: The current criteria for definition of partial GHD in young adults are still a subject of debate.

Objectives: To re-investigate anterior pituitary function in young adults with congenital childhood-onset GHD associated with structural hypothalamic-pituitary abnormalities and with "normal" GH response at the time of first re-assessment of GH secretion.

Design and Setting: This was a prospective explorative study conducted in a University research hospital.

Patients and Methods: Thirteen subjects with a mean age of 17.2 ± 0.7 years and a peak GH after insulin tolerance test (ITT) higher than 5 µg/L were recruited from a cohort of 42 patients with childhood-onset GHD and ectopic posterior pituitary at MRI. GH secretion after ITT and GHRH plus Arginine, IGF-I concentration and BMI, waist circumference, blood pressure, total cholesterol and fibrinogen were evaluated at baseline and at two-year follow-up.

Results: At mean age of 19.2 ± 0.7 years, the mean peak GH response decreased significantly after ITT (P = 0.00001) and GHRH plus Arginine (P = 0.0001). GH peak values after ITT and GHRH plus Arginine were less than 5 µg/L and 9 µg/L in 10 and 8 patients, respectively. Additional pituitary defects were documented in 8 patients. Significant changes were found in the values of IGF-I SDS (P = 0.0026), waist circumference (P = 0.00001), serum total cholesterol (P = 0.00001) and serum fibrinogen (P = 0.0004).

Conclusions: The results of this study underline the importance of further re-assessment of pituitary function in young adults with GHD of childhood-onset and post-stimulation GH responses suggestive of partial GHD.