Circadian rhythmicity of growth hormone at high altitude in man

Circulatory levels of growth hormone (GH) were estimated at 0600 h, 1200 h, 1800 h and 2400 h in each of 10 subjects of sea level residents (SLR) in New Delhi (226 m) and in high altitude natives (HAN) settled at an altitude of 3650 m. Both in SLR and HAN the GH secretion showed an identical pattern, the values were lowest at 0600 h and highest at 2400 h. Nevertheless, in HAN the GH levels at different timings of the day were found to be significantly higher than in SLR.