Oestrogen blood tests

RECOMMENDATION:

• Oestrogen (estradiol) blood levels are not routinely helpful and can be misleading.
• These blood tests are prone to error and can be influenced by many things including the timing of dosing, type of assay used, route of administration and background menopausal status of the woman.
• Results are unlikely to be indicative of average levels over the preceding 24-hours.

LIMITATIONS TO SEROLOGICAL TESTING:

If blood tests are performed, clinicians should remain mindful of the limitations of serological testing. Particularly that:

• If the woman is perimenopausal, the level of estradiol will vary greatly in different parts of her menstrual cycle (see table above).
• For users of oral oestrogen, the major circulatory metabolite is estrone meaning blood tests for estradiol are unreliable.
• The Lenzetto spray contains a chemical called octisalate. It is not known if this interferes with blood test results.
• Estradiol levels will vary considerably according to the time of application of gels.

WHEN MIGHT IT BE APPROPRIATE TO CHECK ESTRADIOL LEVELS?

• Where higher doses of oestrogen are being considered, a baseline estradiol level might be helpful to confirm reduced absorption and to check that levels are not elevated at baseline.
• Some women with premature ovarian insufficiency (POI) have minimal symptoms despite being oestrogen deficient and in this situation it would be reasonable to check a serum estradiol level (where the transdermal route is used), to confirm absorption. The aim of hormone replacement in these women should be to achieve mean physiological estradiol levels, as found in the serum of women with normal menstrual cycles. ESHRE guidelines state that this is between 180-370pmol/L.