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Stimulation of growth hormone secretion in children with X-linked hypophosphatemia
1University of Texas Southwestern Medical Center, Dallas 75235-9063, USA.
Insights
Short stature in X-linked hypophosphatemia is not caused by growth hormone (GH) deficiency. Studies show GH levels are normal and respond adequately to stimulation, ruling out GH/IGF-I secretory defects as the cause.
Area of Science:
- Pediatric Endocrinology
- Genetics
- Metabolic Bone Disease
Background:
- X-linked hypophosphatemia (XLH) presents with hypophosphatemia, vitamin D deficiency, and rickets.
- Despite treatment, XLH patients often exhibit short stature.
- The role of growth hormone (GH) deficiency in XLH-related short stature is unclear.
Purpose of the Study:
- To investigate potential growth hormone (GH) deficiency in children with X-linked hypophosphatemia.
- To assess GH response to pharmacological stimulation in XLH patients.
Main Methods:
- Studied 16 children diagnosed with X-linked hypophosphatemia.
- Measured basal GH, IGF-I, and IGFBP-3 levels.
- Administered sequential paired pharmacological stimulation (L-dopa and arginine hydrochloride) to assess GH secretion.
Main Results:
- Basal GH levels were 3.8 +/- 0.7 ng/ml, IGF-I was 225 +/- 38 ng/ml, and IGFBP-3 was 3.0 +/- 0.2 mg/l.
- All patients demonstrated a significant rise in serum GH (>7 mg/ml) after stimulation.
- This indicates normal GH secretory capacity in response to stimuli.
Conclusions:
- Short stature in X-linked hypophosphatemia is not attributable to a growth hormone (GH) or insulin-like growth factor-I (IGF-I) secretory defect.
- Further research is needed to identify the underlying causes of short stature in XLH patients despite adequate metabolic control.
Abstract:
X-linked hypophosphatemia is characterized by low serum phosphorus, relative vitamin D deficiency and rickets. Despite adequate metabolic control with oral phosphate and vitamin D therapy, patients with X-linked hypophosphatemia have short stature. Whether growth hormone (GH) deficiency plays a role in short stature in patients with X-linked hypophosphatemia is not known. The purpose of this report was to investigate the response of GH to sequential paired pharmacological stimulation in patients with X-linked hypophosphatemia. Basal GH was 3.8 +/- 0.7 ng/ml, insulin-like growth factor-I (IGF-I) was 225 +/- 38 ng/ml and IGF binding protein-3 was 3.0 +/- 0.2 mg/l in 16 children studied with X-linked hypophosphatemia. In response to L-dopa and arginine hydrochloride stimulation, serum GH rose to above 7 mg/ml in all patients. Thus, the short stature in patients with X-linked hypophosphatemia is not due to a GH/IGF-I secretory defect.