Endocrine Abstracts

JOINT1030

Introduction: Growth hormone (GH) deficiency is commonly diagnosed using stimulation tests such as insulin hypoglycemia or the GH-releasing hormone-arginine test. However, these tests are burdensome and require intravenous access. Macimorelin, an oral GH stimulation test, offers an alternative but is unavailable in many countries, highlighting the need for accessible, non-invasive oral options. Urea, the end product of protein metabolism, is commonly used as an oral treatment for hyponatremia. Since GH promotes protein synthesis and reduces urea production, we hypothesized that high urea levels may stimulate GH secretion via feedback regulation. Therefore, this study investigates whether oral urea could serve as an alternative stimulation test for diagnosing GH deficiency.

Methods: This is a secondary analysis of a double-blind, randomized, placebo-controlled cross-over trial in 22 healthy adults. Participants presented for two visits in the morning after an overnight food fasting and a two-hour fluid restriction. They received a single weight-adapted dose of oral urea (0.5 g/kg body weight; minimum 30g, maximum 45 g) or placebo in random order. Serum GH was measured at baseline, 60 and 120 minutes. The primary endpoint was the serum GH levels after ingestion of urea vs placebo.

Results: Of 22 healthy adults, 12 (55%) were female, with a median [IQR] age of 27 years [26, 32] and a body mass index of 23.3 kg/m² [21.6, 25.8]. Before urea ingestion, GH at baseline was 0.83 µg/l [0.28, 5.75], decreased to 0.38 µg/l [0.20, 2.46] after 60 minutes, and increased to 1.00 µg/l [0.71, 2.34] after 120 minutes. Before placebo ingestion, GH at baseline was 0.93 µg/l [0.38, 5.34], decreased to 0.38 µg/l [0.16, 1.51] after 60 minutes, and increased to 0.73 µg/l [0.18, 1.59] after 120 minutes.

Conclusion: Our study demonstrated no relevant changes in serum GH after the ingestion of urea in comparison with placebo. These findings suggest that urea does not stimulate GH secretion and cannot be used as a stimulation test for GH deficiency.