What is happening in the body in pre-menopause

As the woman approaches the end of her child-bearing years the number of follicles in the ovary has reduced from 250,000 at puberty4 to about 10,000 follicles at the age of 45.2 At the menopause many of these remaining follicles become atretic (degenerate) without ever achieving an ovulation. This reduced ovarian activity results in decreased levels of the ovarian hormones, oestrogen and progesterone which is the basis of the symptoms of pre-menopause. This can result in LONG  cycles or SHORT cycles.

Long cycles

The long cycle may be one with no ovulation  (anovulatory)  or one with delayed ovulation.

Short cycles

The short cycle may be due to either:

  • a short luteal phase or
  • a short follicular phase and early ovulation,2 or
  • the LUF syndrome (luteinized unruptured follicle syndrome).3

FSH is increased

FSH secretion by the pituitary gland is increased due to the absence of the follicular fluid peptide inhibin B, as during normal reproductive life the secretion of FSH is inhibited by inhibin B. The earliest endocrine change marking entry into the menopausal transition is a major fall in inhibin B.1 However inhibin B is a very difficult and relatively unavailable assay and would not contribute to the staging system.5


  1. Liu JH, Gass ML; ‘Management of the perimenopause’; 2006; Pub. McGraw-Hill, ISBN 0-0-142281-1
  2. Flynn A, Worthington W; ‘Teachers Training Manual’; ‘symptothermal multiple index method’ of natural family planning.
  3. Brown JB; ‘Types of ovarian activity in women and their significance: the continuum (a reinterpretation of early findings)’; Human Reproduction Update; 2011; Vol 17; No 2; p141-158. (this is a classic article which gives a greater understanding of the menstrual cycle throughout the reproductive life of the woman).
  4. Alvero Ruben, Schlaff William D; ‘Reproductive endocrinology and infertility, The Requisites in Obstetrics and Gynecology’; 2007, page 229; ISBN-13:978-0-323-04054-9
  5. Soules MR, Sherman S, Parrot E et al; Executive summary: Stages of Reproductive Aging Workshop (STRAW). Fertil Steril. 2001; 76: 874