Hormones

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Oestrogen is produced from the developing follicle within the female ovary. Development of the follicles with resultant rise and fall in oestrogen production commences around puberty and increasing levels results in stimulation/thickening of the endometrium - uterine lining. When the oestrogen levels fall as the follicle shrinks during each cycle there is a withdrawal bleed and this is called a menstrual period. 

In the early stages after puberty ovulation follicle is not usually achieved and this can result in irregular menstrual bleeds for a few years until true follicular development begins to occur.

The rise and fall of oestrogen irregularly due to the rapid production of follicles can lead to similarly irregular uterine bleeding which can cause problems in day to day life.

Falling levels of oestrogen however can lead to symptoms including vasomotor/adrenaline such as flushes and sweats, poor quality light sleep, low mood and fatigue. When the cycle is regular this can occur premenstrually with the symptoms improving when the oestradiol level lifts at the end of each menstrual bleed.

If a new follicle does not develop then the low oestrogen symptoms may persist for a while or in some cases remains throughout the menstrual cycle. If the onset of symptoms is difficult to control then it may be useful to downregulate the cycle to use addback oestradiol continuously to give a more steady level of oestrogen rather than rely on the fluctuant nature of hormone production from variable follicle production.