Time series analysis of biologically active luteinizing hormone concentrations during different stages of the...

The biologically active luteinizing hormone concentrations (as measured by testosterone production by mouse Leydig cells in response to LH) were measured in integrated hourly blood samples collected over 24-hour study periods during different stages of the menstrual cycle from a group of regularly cyclic women. Time series analyses were used to analyse the ultradian rhythms in each individual 24-hour LH profile. Fast Fourier transform (FFT) showed the presence of several ultradian rhythms with different periodicities (varying from 4.4 to 22 hours) in most of the LH profiles. In some of the LH profiles several ultradian rhythms appeared to co-exist. The commonest significant rhythm as detected by the FFT had a periodicity of 7-9 hours during both the follicular phase (40% of the subjects) and the mid cycle (50% of the subjects) and a periodicity of 5-7 hours during the luteal phase (44% of the subjects).