Oestradiol is a steroid hormone with a molecular weight of 272. It is secreted mainly by the ovary, but small amounts are produced by the adrenals and testis, so that in males and in post menopausal females’ Oestradiol is always present at low concentrations. During the normal menstrual cycle, the graafian follicle secretes Oestradiol into the follicular atrum and the ovarian vein. The levels gradually increase in the follicular phase, reaching a peak shortly before ovulation. After ovulation the corpus luteum secretes oestradiol, maintaining the levels at about half of the mid-cycle peak. If pregnancy does not ensue the levels fall and the next menstrual cycle begins.At puberty, Oestradiol levels rise producing the normal development of the secondary sexual characteristics and mammary glands.
Oestradiol measurements are of value in: – induction of ovulation, amenorrhea, testicular dysfunction, gonadal dysgenesis and monitoring Hormone Replacement Therapy. Pathologically high values are seen in ovarian tumours, adrenal tumours, precocious puberty, gyneacomastia and testicular tumours with adrenal hyperplasia. Low values are found in Sheenans syndrome, ovarian insufficiency, hyperprolactinaemia, polycystic ovaries and anorexia nervosa.
Women undergoing fertility treatment are initially given a GnRH analogue (either by nasal spray or by subcutaneous injection) which completely suppresses endogenous production of LH and FSH. This effectively “down regulates” the ovaries so that spontaneous development of follicles is prevented. After several weeks of this treatment in the absence of developing follicles the Oestradiol level should be less than 250pmol/L. If this is not the case then further treatment with GnRH is pursued until the Oestradiol level falls below 250 pmol/L. The women are then given metrodin injections (purified urinary FSH) which stimulates follicular development. The developing follicles secrete Oestradiol, which can then be measured. The rate of increase in the level of Oestradiol indicates the number of developing follicles. The Oestradiol level in conjunction with the ovarian ultrasound scan data to determine the amount of metrodin to be given. The normal positive feedback of high Oestradiol levels on the hypothalamus/pituitary to produce a surge in LH to initiate ovulation is prevented by the GnRh analogue. When Oestradiol levels are sufficiently high (800 – 1000 pmol/L per mature follicle and greater than 3500 pmol/l) HCG is given (10,000 units) which mimics natural LH and starts the process of ovulation. If the oestradiol is greater than 13000 pmol/l it means that too many follicles have developed. In this event the patient is not given HCG. This is to prevent the life-threatening hyper stimulation syndrome from developing.
Children: Less than 130 pmol/L
Males: Less than 146 pmol/L
Follicular: 72 – 529 pmol/L
Ovulatory: 235 – 1309 pmol/L
Luteal: 205 – 786pmol/L
Post-menopause: Less than 118 pmol/L
- Three patient identifiers from
- N.H.S. number
- Unit Number