From the Research
No, progesterone levels are not artificially lowered when estradiol levels exceed 120 pg/mL in postmenopausal women on hormone replacement therapy (HRT). The two hormone measurements are independent of each other in laboratory testing. When a woman takes estrogen as part of HRT, her estradiol levels will increase, but this does not directly interfere with the laboratory measurement of progesterone. If a woman is taking both estrogen and progesterone (or progestin) as part of her HRT regimen, both hormone levels will reflect the supplementation. However, the timing of blood draws is important - progesterone levels fluctuate based on when the medication was last taken, especially with oral progesterone which has a short half-life. For accurate assessment of hormone levels on HRT, blood should ideally be drawn 4-6 hours after taking oral medications or at the midpoint between applications for transdermal methods.
According to the most recent and highest quality study available, 1, hormone therapy for postmenopausal women with an intact uterus should comprise both estrogen and progestogen to reduce the risk of endometrial hyperplasia. This study, published in 2012, found that unopposed estrogen is associated with increased risk of endometrial hyperplasia at all doses, and durations of therapy between one and three years. In contrast, the risk of endometrial hyperplasia with hormone therapy comprising low-dose estrogen continuously combined with a minimum of 1 mg norethisterone acetate or 1.5 mg medroxyprogesterone acetate is not significantly different from placebo.
Key points to consider:
- The risk of endometrial hyperplasia is increased with unopposed estrogen therapy, but this risk can be mitigated with the addition of progestogen 1.
- The timing of blood draws is crucial for accurate assessment of hormone levels on HRT, with progesterone levels fluctuating based on when the medication was last taken 1.
- For women with a uterus, hormone therapy should comprise both estrogen and progestogen to reduce the risk of endometrial hyperplasia 1.
If you're concerned about your hormone levels on HRT, discuss the results with your healthcare provider who can interpret them in the context of your specific regimen and symptoms.