FSH and LH are secreted in a pulsatile way. Pulses are roughly every 90 minutes at first but become a little slower in the second half of your cycle. The peak of each pulse is also higher in the second half of the cycle and very much higher just before ovulation (14 days before your period). For these reasons values are usually taken during the first five days of the cycle as they are easier to interpret. As a rule of thumb, values in double figures (i.e. 10iu/litre or greater) would cause concern.