Serum oestradiol does not change proportionally in response to oral oestrogens

Oral menopausal hormone therapy (MHT) using various formulations and doses of oestrogen does not seem to proportionally impact serum oestradiol levels, a recent study has found.

Researchers conducted a cross-sectional investigation of 344 postmenopausal women who were on oral MHT. Formulations included oestradiol hemihydrate (EH), oestradiol valerate (EV), and conjugated oestrogen (CE); doses were 1 or 2 mg for oestradiol-containing MHTs, and 0.45 or 0.625 mg for CE formulations. Those who had recently changed MHT regimens, used non-oral interventions, or were smokers were excluded from the analysis.

Serum oestradiol spiked with increasing MHT dose, though not proportionally so. For instance, instead of doubling, the 2-mg dose of oestradiol (EH and EV combined) resulted in a 60-percent jump in serum oestradiol relative to the 1-mg dose (107.6 vs 65.8 pg/mL).

Similarly, serum oestradiol was also around 60-percent higher after the higher MHT oestradiol dose vs the 0.45-mg CE dose (107.6 vs 60.1 pg/mL). A similar effect was reported for CE at 0.625 mg, though to a slightly lesser degree (107.6 vs 76.8 pg/mL).

“[A]lthough serum oestradiol level increased with dose of oestrogen, amount of increase was not directly proportional to dose of oestrogen,” the researchers said, “in particular, for oral oestradiol, doubling the oestrogen dose from 1 to 2 mg presented an increase of approximately 60 percent instead of doubling the serum oestradiol level.”

“This finding suggests that ‘low-dose’ oestrogen might be adequate as an initial MHT. Then, clinicians can do upward titration based on clinical response,” they added.