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Urinary growth hormone excretion during puberty in type 1 (insulin-dependent) diabetes mellitus
P Hourd1, J A Edge, D B Dunger
1North East Thames Regional Immunoassay Unit, St Bartholomew's Hospital, London, UK.
Insights
Urinary growth hormone (GH) excretion reflects circulating levels in children and increases during puberty. Diabetic children show higher urinary GH excretion than normal children, but this may be affected by kidney function markers.
Area of Science:
- Pediatric endocrinology
- Diabetology
- Nephrology
Background:
- Growth hormone (GH) plays a crucial role in pubertal development.
- Assessing endogenous GH levels is important in pediatric populations, especially those with chronic conditions like Type 1 diabetes.
- Urinary GH excretion is a potential non-invasive marker for circulating GH levels.
Purpose of the Study:
- To investigate urinary growth hormone (GH) excretion during puberty in children with Type 1 diabetes mellitus (T1DM) compared to healthy controls.
- To determine the relationship between urinary GH excretion and plasma GH levels.
- To explore correlations between urinary GH excretion and markers of kidney function and glycemic control in diabetic children.
Main Methods:
- A cross-sectional study measured overnight urinary GH excretion using a direct immunoradiometric assay.
- Plasma GH concentrations were measured to validate urinary GH as a marker.
- Urinary albumin, retinol binding protein, and N-acetyl-beta-D-glucosaminidase were quantified in diabetic children.
Main Results:
- Urinary GH excretion significantly correlated with plasma GH levels in both normal and diabetic children.
- Urinary GH excretion increased during puberty, with distinct peaks in boys and girls.
- Diabetic children exhibited higher urinary GH excretion across all pubertal stages compared to controls.
- Urinary GH showed weak correlations with urinary albumin, retinol binding protein, and N-acetyl-beta-D-glucosaminidase, and no relation to HbA1c.
Conclusions:
- Urinary GH excretion is a reliable indicator of endogenous GH levels during puberty in both healthy and diabetic children.
- Diabetic children demonstrate elevated urinary GH excretion, suggesting potential alterations in GH regulation or clearance.
- Caution is advised when interpreting urinary GH in diabetic patients with compromised kidney function due to increased albumin and retinol binding protein excretion.
Abstract:
The excretion of urinary growth hormone was measured by a highly sensitive direct immunoradiometric assay in a cross-sectional study during puberty in 70 children with Type 1 (insulin-dependent) diabetes mellitus and 94 normal children. In normal children (n = 24) and diabetic children (n = 17) overnight urinary growth hormone excretion correlated significantly with the mean overnight plasma concentration (r = 0.70, p less than 0.001, and r = 0.70, p less than 0.001), indicating that urinary GH excretion reflects the circulating endogenous GH level. Overnight urinary growth hormone excretion increased during puberty. In normal and in diabetic children there was a peak in boys at genital stage 4 (both p less than 0.01), and in girls at breast stage 2 (both p less than 0.02). The diabetic children excreted more urinary growth hormone than the normal children at every pubertal stage. Excretion of albumin, retinol binding protein and N-acetyl-beta-D-glucosaminidase was measured in urine from 38 diabetic children. Urinary growth hormone correlated weakly with urinary albumin (r = 0.49, p less than 0.01), retinol binding protein (r = 0.42, p less than 0.01), and N-acetyl-beta-D-glucosaminidase (r = 0.43, p less than 0.01). Urinary GH excretion was not related to blood glucose control (HbA1) in boys (n = 31) or girls (n = 39). The measurement of urinary growth hormone provides an assessment of endogenous growth hormone during puberty in normal and diabetic children. However, caution must be exercised in interpreting urinary growth hormone data from diabetic patients with increased excretion of albumin and retinol binding protein.