Circadian variations in plasma LH and FSH in juvenile and adult male mice.

Experiments were performed to ascertain circadian fluctuations in plasma levels of LH and FSH in juvenile and adult male mice. Animals under natural lighting (11 h day/13 h night) were killed at 1-hour intervals over a 24-hour period. There were large variations in plasma LH concentrations between animals sacrificed within each killing period. Baseline LH levels (values lower than 60 ng/ml) showed a significant 24-hour periodicity in adult males. FSH concentrations exhibited significant diurnal variations in juvenile and adult males. There was significant influence of age on the temporal pattern and 24-hour mean plasma hormone levels.