ESPE Abstracts

Background: A small subgroup of children with isolated growth hormone deficiency (IGHD) develop central hypothyroidism (CH) during GH treatment. Prognostic parameters are still unclear.

Objective and hypothesis: Long-term evaluation of children with initial diagnosis of IGHD to identify those with an unmasking CH under GH treatment. IGHD was diagnosed in children with short stature, low height velocity, retarded bone age, pathological low IGF-1 and two GH stimulation tests with a GH peak < 8 ng/ml.

Methods: Retrospective analysis of all patients with IGHD diagnosed between 1995 and 2022 in our center. Patients with septo-optic dysplasia, neurosecretory dysfunction and CH at start of GH treatment were excluded. fT4- and TSH-levels were measured by chemiluminescent immunoassay (CLIA). CH was defined by fT4 < 11 pmol/l in two independent consecutive measurements. Brain MRI was evaluated for the presence of pituitary malformation.

Patients: 200 children (141 males) with initial diagnosis of IGHD were identified. At onset of GH treatment, mean age was 5.9 years (+/- 2.2), mean height -3.2 SDS (+/- 0.9) and mean weight -2.2 SDS (+/- 0.7). 56 patients (28 %) showed a pituitary malformation. Median follow up time after onset of GH treatment was 13.4 years (0.4 – 25.5).

Results: In 4 % of the patients (n=8) a CH was unmasked during GH treatment. The lowest fT4 level before L-T4 treatment was median 10 pmol/l (7.8 – 10.4). Median time period to diagnosis of CH after initiation of GH treatment was 9 months (6 – 38). CH was associated with a significant pituitary malformation in 5 patients. The likelihood of the occurrence of CH in the presence of a pituitary malformation was 8.9 % (5/56) vs. 2.1 % (3/144) in its absence (P= 0.027).

Conclusion: Central hypothyroidism occurred in 4 % of children with initial diagnosis of IGHD under GH treatment; in presence of a pituitary malformation occurrence of CH was significantly more likely. Our data emphasize the need for regular measurement of fT4 and TSH over the course of GH treatment, especially in patients with pituitary malformations.