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Infradian rhythms in urinary growth hormone excretion
N K Thalange1, M S Gill, L Gill
1Department of Child Health, Royal Manchester Children's Hospital, Pendlebury, United Kingdom.
The Journal of Clinical Endocrinology and Metabolism
|January 1, 1996
Summary
This study reveals distinct rhythms in growth hormone (GH) excretion in children, with daily, weekly, and monthly fluctuations. Understanding these patterns is crucial for studying the relationship between GH and growth.
Area of Science:
- Pediatric Endocrinology
- Chronobiology
- Growth Hormone Research
Background:
- Urinary growth hormone (GH) excretion exhibits significant day-to-day variability.
- Previous studies have noted infradian variations in GH output, but longer-term rhythms remain under-investigated.
Purpose of the Study:
- To investigate the existence of longer-term rhythms in endogenous GH secretion.
- To explore the potential relationship between GH excretion patterns and growth in prepubertal children.
Main Methods:
- Serial overnight urinary GH estimations were performed in eight normal prepubertal children over 90-365 days.
- Urinary GH was measured via immunoradiometric assay after dialysis, expressed as total amount or GH/creatinine ratio.
- Pulse counting and time-series analysis were employed to assess GH excretion patterns.
Main Results:
- Urinary GH excretion showed significantly greater variability (median CV, 46%) than creatinine (median CV, 25%).
- Marked month-to-month variations in baseline urinary GH were observed in all children.
- High-frequency GH pulses (3-5 day periods) were detected, along with significant weekly rhythms (2.6 and 4.1 weeks) in longer-term follow-ups.
Conclusions:
- Urinary GH excretion comprises three components: long-term monthly fluctuations, short-term daily pulses, and intermediate weekly rhythms.
- These findings represent a foundational step in understanding GH excretion dynamics and their link to growth.