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Growth hormone secretion in poorly growing children with renal hypophosphataemic rickets
G Saggese1, G I Baroncelli, S Bertelloni
1Department of Pediatrics, University of Pisa, Italy.
Insights
Growth hormone (GH) secretion and insulin-like growth factor-I (IGF-I) levels were normal in children with renal hypophosphataemic rickets, despite poor growth. Treatment did not alter these parameters, suggesting GH and IGF-I are not primary drivers of growth failure in this condition.
Area of Science:
- Pediatric Endocrinology
- Pediatric Nephrology
- Metabolic Bone Diseases
Background:
- Renal hypophosphataemic rickets is a condition causing poor growth in children.
- Growth hormone (GH) and insulin-like growth factor-I (IGF-I) are crucial for normal growth.
- The role of GH-IGF-I axis in growth failure associated with rickets is not fully understood.
Purpose of the Study:
- To evaluate GH secretion and IGF-I levels in children with renal hypophosphataemic rickets.
- To assess the relationship between GH-IGF-I axis and growth parameters in these patients.
- To investigate the impact of treatment on GH and IGF-I levels.
Main Methods:
- Studied 12 children with renal hypophosphataemic rickets and 11 healthy controls.
- Assessed GH secretion using provocative pharmacological stimuli (levodopa or insulin tolerance test).
- Measured baseline serum IGF-I levels and various biochemical markers of phospho-calcium metabolism.
Main Results:
- All patients and controls exhibited normal GH responses to stimuli.
- Mean GH concentrations (MGHC), GH pulse characteristics, and IGF-I levels were comparable between patients and controls.
- No significant differences in growth parameters or biochemical markers were observed, irrespective of MGHC or height-SDS subgroups.
Conclusions:
- The GH-IGF-I axis appears to function normally in children with renal hypophosphataemic rickets, even with poor growth.
- Growth failure in this condition is likely not primarily due to impaired GH secretion or IGF-I production.
- Current treatment with 1,25-dihydroxy-vitamin D3 and phosphate does not significantly alter GH-IGF-I axis parameters.
Abstract:
We evaluated growth hormone (GH) secretion and baseline serum free insulin-like growth factor-I (IGF-I) levels in 12 poorly growing patients (5 males and 7 females; age 1.6-12.5 years, median 6.4) with renal hypophosphataemic rickets treated with 1,25-dihydroxy-vitamin D3 plus inorganic oral phosphate salts. Eleven healthy normally growing children (6 males and 5 females; age 3.1-10.8 years, median 6.6) were studied as control group. All patients had a normal GH response (GH peak > or = 10 micrograms/l) to at least one provocative pharmacological stimulus (levodopa or insulin tolerance test), as well as all the controls. Mean growth hormone concentrations (MGHC), mean pulse amplitude, number of GH peaks above 5 micrograms/l, and IGF-I values overlapped between patients and controls, even though four patients had MGHC below the lower limit of MGHC of controls. In these patients, however, height-SDS, serum calcium, phosphate, alkaline phosphatase, intact parathyroid hormone, 1,25-dihydroxyvitamin D concentrations and maximum tubular phosphate reabsorption/glomerular filtration rate ratio did not differ in respect to the patients who showed MGHC in the range of controls (n = 6). MGHC IGF-I and biochemical parameters of phospho-calcium metabolism did not differ when the patients were subdivided in two groups on the basis of the median (-2.4) of height-SDS. No relationship was found between MGHC or IGF-I and height-SDS or growth velocity-SDS. Height-SDS and years of treatment or age at which therapy was started were not related.(ABSTRACT TRUNCATED AT 250 WORDS)