Infradian Rhythm

• Infradian rhythms repeat less than once every 24hrs e.g. the menstrual cycle.
• The menstrual cycle is regulated by hormones (endogenous pacemakers). The rise of oestrogen causes ovulation, the release of an egg from the ovaries, coordinated by the pituitary gland. Usually lasting 16 - 32 hrs when oestrogen levels are at their peak. Hormones also stimulate the uterus for fertilisation and leads to menstration. The cycle is around 29 days