Progesterone Options for Hormone Replacement Therapy
Micronized progesterone (MP) is the first-choice progestin for HRT due to its lower risk of cardiovascular disease and venous thromboembolism compared to synthetic progestins, with second-line options including medroxyprogesterone acetate (MPA), dydrogesterone, and norethisterone. 1
First-Line Progesterone Option
Micronized Progesterone (MP) is the preferred progestin because it demonstrates superior cardiovascular and thrombotic safety profiles while providing adequate endometrial protection. 1
Dosing Regimens for Micronized Progesterone:
Sequential (Cyclical) Regimens:
- 200 mg oral or vaginal MP daily for 12-14 days every 28 days when combined with continuous estrogen 1
- This regimen induces predictable withdrawal bleeding 1
- Vaginal administration achieves comparable efficacy with potentially fewer systemic side effects 2
Continuous Combined Regimens:
- Continuous daily MP can be used to avoid withdrawal bleeding, though specific dosing is less well-established in the guidelines 1
Second-Line Synthetic Progestin Options
When MP is unavailable or not tolerated, the following synthetic progestins are acceptable alternatives: 1
Medroxyprogesterone Acetate (MPA):
Sequential regimens: 10 mg daily for 12-14 days per month 1
Continuous regimens: 2.5 mg daily 1
Dydrogesterone:
Sequential regimens: 10 mg daily for 12-14 days per month 1
Continuous regimens: 5 mg daily 1
- Dydrogesterone shows neutral effects on vascular and metabolic systems, potentially maintaining estradiol's cardioprotective benefits 3
Norethisterone:
Continuous regimens: Minimum of 1 mg daily 1
Route-Specific Progestin Delivery Options
Transdermal Patches:
Combined estradiol + levonorgestrel patches are recommended as first choice for improved compliance: 1
- Sequential patches: 50 μg estradiol for 2 weeks, followed by 50 μg estradiol + 10 μg levonorgestrel for 2 weeks 1
- Continuous patches: 50 μg estradiol + 7 μg levonorgestrel daily without interruption (avoids withdrawal bleeding) 1
Vaginal Administration:
Vaginal MP 200 mg daily for 12-14 days every 28 days provides equivalent endometrial protection to oral administration 1
- Vaginal progesterone gel (Crinone 4%, 45 mg daily) can be used cyclically (days 1-10 monthly) or twice weekly for continuous combined regimens 2
- 91.9% of women achieve predictable withdrawal bleeding with cyclical vaginal progesterone 2
- 80.6% remain amenorrheic with twice-weekly vaginal progesterone in continuous combined regimens 2
Oral Tablets:
Combined oral formulations containing 1-2 mg estradiol with progestin are available in both sequential and continuous formulations: 1
- Estradiol + dydrogesterone
- Estradiol + MPA
- Estradiol + dienogest (2 mg for continuous regimens) 1
Critical Clinical Considerations
Avoid progestins with anti-androgenic effects in women with low testosterone levels or sexual dysfunction, as these can worsen hypoandrogenism. 1
Endometrial protection is mandatory in all women with an intact uterus receiving estrogen therapy; unopposed estrogen increases endometrial cancer risk. 4
Choice between sequential vs. continuous regimens depends on patient preference regarding withdrawal bleeding: 1
- Sequential regimens induce predictable monthly bleeding
- Continuous combined regimens aim for amenorrhea
Natural progesterone formulations (micronized progesterone) are chemically identical to endogenous progesterone, allowing more physiological effects compared to synthetic progestins. 5