Context: Growth hormone (GH) replacement therapy in GH deficient (GHD) patients is usually continued until adult height despite the fact that most of these subjects display a normal secretion when retested at the end of growth. Puberty is the most likely time for normalization of GH secretion.

Objectives: To establish the characteristics and the percentage of the subjects with isolated GHD who normalized secretion at puberty and to compare their statural outcome with that of the subjects with persistent deficiency treated also after retesting.

Designand setting: prospective, non randomized open label study conducted in a University research hospital.

Patients and Intervention: 69 subjects (40 M, 29 F) with a diagnosis before puberty of isolated GHD by means of arginine and l-dopa tests were re-evaluated with the same tests after at least 2 yr of therapy and after puberty onset. If GH peak at retesting was > 10 µg/liter therapy was withdrawn.

Main outcome measures. Percentage and characteristics of normalized subjects at retesting, outcome of treatment in the subjects treated or untreated to adult height, and factors predictive of growth outcome.

Results. At retesting 44 subjects (63.7%) confirmed a GH peak < 10 µg/liter (24/40 M and 20/29 F). Apart from a less delayed bone age at diagnosis in females, the subjects with confirmed GHD were not different at diagnosis from the other group for height deficit at diagnosis, 1^st year growth response to GH, age and height at puberty onset, height and IGF-I at retesting. Mean adult height was 165.1 ± 4.5 cm in the male group treated till adult height vs. 164.0 ± 3.4 cm in the group who suspended therapy at retesting. Mean adult height was 153.2 ± 4.1 cm in the female group treated till adult height vs. 152.9 ± 5.2 cm in the group that suspended therapy at retesting. As regards the parameters expressing the final outcome, the only difference was found in the mean increment adult height-target height SDS in favor of the male group treated till adult height. In both sexes therapy duration and GH levels at diagnosis and at retesting were unrelated to adult height parameters and to height increments during the period of observation.

Conclusions: One third of our GHD subjects diagnosed before puberty presented a normal secretion at puberty. The withdrawal of GH therapy in these subjects after retesting was not associated with a catch down growth and they obtained an adult height similar to that obtained by the GHD subjects treated till adult height. It seems convenient, in subjects with non severe GHD, to retest GH secretion at mid puberty and to withdraw treatment for the subjects that are no longer deficient.