Micronized progesterone vs medroxyprogesterone acetate
Experts in menopause medicine have suggested that in postmenopausal women micronized progesterone has a better pattern of benefits and fewer risks than medroxyprogesterone acetate.10,11 For example, in the E3N observational study of hormones and breast cancer risk, among 80,377 French postmenopausal women followed for a mean of 8 years, the combination of transdermal estradiol plus oral micronized progesterone was associated with no significantly increased risk of breast cancer (relative risk [RR], 1.08, 95% confidence interval [CI], 0.89–1.31) compared with never users of postmenopausal hormone therapy.12 By contrast, the combination of oral estrogen plus medroxyprogesterone acetate was associated with an increased risk of breast cancer (RR, 1.48; 95% CI, 1.02–2.16) compared with never users of postmenopausal hormone therapy. The E3N study indicates that micronized progesterone may have a more favorable breast health profile than medroxyprogesterone acetate.12
Norethindrone acetate monotherapy is not commonly prescribed for the treatment of menopausal hot flashes. However, a large clinical trial has demonstrated that norethindrone acetate effectively suppresses hot flashes in women with endometriosis treated with depot leuprolide acetate (LA). In one trial 201 women with endometriosis were randomly assigned to 12 months of treatment with13:
- LA plus placebo pills
- LA plus norethindrone acetate (NEA) 5 mg daily
- LA plus NEA 5 mg daily plus conjugated equine estrogen (CEE) 0.625 mg daily, or
- LA plus NEA 5 mg daily plus CEE 1.25 mg daily.
The median number of hot flashes in 24 hours was 6 in the LA plus placebo group and 0 in both the LA plus NEA 5 mg daily group and the LA plus NEA 5 mg plus CEE 1.25 mg daily group. This study demonstrates that NEA 5 mg daily is an effective treatment for hot flashes.
In the same study, LA plus placebo was associated with a significant decrease in lumbar spine bone mineral density. No significant decrease in bone mineral density was observed in the women who received LA plus NEA 5 mg daily. This finding indicates that NEA 5 mg reduces bone absorption caused by hypoestrogenism. In humans, norethindrone is a substrate for the aromatase enzyme system.14 Small quantities of ethinyl estradiol may be formed by aromatization of norethindrone in vivo,15,16 contributing to the effectiveness of NEA in suppressing hot flashes and preserving bone density.
Progestin: The estrogen alternative to hot flashes
For postmenopausal women with moderate to severe hot flashes, estrogen treatment reliably suppresses hot flashes and often improves sleep quality and mood. For postmenopausal women with a contraindication to estrogen treatment, progestin-only treatment with micronized progesterone or norethindrone acetate may be an effective option.