How to Use Intermittent (Cyclical) Progesterone Dosing in HRT
For women with an intact uterus receiving estrogen therapy, administer progesterone for a minimum of 10-14 days per month at 200 mg daily (oral micronized progesterone) or equivalent progestogen doses to provide endometrial protection. 12
Standard Cyclical Dosing Protocol
The evidence-based approach for intermittent progesterone administration follows this framework:
Monthly Cyclical Regimen (First-Line)
- Estrogen: Administer continuously throughout the month
- Progesterone: Add for 10-14 consecutive days each 28-day cycle 12
- Dose: 200 mg oral micronized progesterone taken at bedtime 33
- Expected outcome: Monthly withdrawal bleeding typically occurs after progesterone is stopped
This regimen carries a Grade A recommendation with strong evidence (BEL 1) from the American Association of Clinical Endocrinologists, demonstrating that this duration and dosing provides adequate endometrial protection against hyperplasia and cancer 12.
Alternative: Long-Cycle Therapy
Progesterone for 14 days every 3 months may be considered to reduce breast exposure to progestogens, though this carries only a Grade B recommendation due to lack of definitive efficacy assessment 12. This approach remains less validated for endometrial protection.
Specific Dosing Details
Oral Micronized Progesterone
- Standard dose: 200 mg daily for 12-14 days per month 334
- Timing: Take at bedtime due to drowsiness/dizziness side effects 3
- Duration validated: Up to 5 years of safe use 4
- Endometrial protection: Proven effective in preventing hyperplasia (6% incidence vs 64% with estrogen alone) 3
Alternative Progestogens (if micronized progesterone unavailable)
- Medroxyprogesterone acetate (MPA): 10 mg daily for 12-14 days per month 55
- Dydrogesterone: 10 mg daily for 12-14 days per month 55
- Norethisterone acetate (NETA): Appropriate doses for 12-14 days monthly 6
Route-Specific Considerations
Transdermal Estrogen + Oral/Vaginal Progesterone
When using transdermal estrogen (patches releasing 50-100 μg daily):
- Add oral progesterone 200 mg daily for 12-14 days every 28 days 55
- Alternative: Vaginal micronized progesterone 200 mg daily for 12-14 days 55
- Vaginal route may provide endometrial protection at 4% gel (45 mg/day) or 100 mg every other day for at least 10 days/month, though this is off-label use 4
Combined Sequential Patches
For improved compliance, sequential combined patches are available:
- 17β-estradiol alone for 2 weeks
- Followed by 17β-estradiol + progestin (e.g., levonorgestrel) for 2 weeks 55
Critical Warnings
Continuous daily progesterone is NOT recommended for standard HRT due to concerns about increased breast cancer risk with continuous progestogen exposure (Grade D recommendation) 11. The intermittent approach reduces progestogen exposure while maintaining endometrial safety.
Important Caveats
- Transdermal progesterone does NOT provide endometrial protection and should not be used 4
- Any abnormal vaginal bleeding requires immediate endometrial evaluation with ultrasound and biopsy 22
- Progesterone capsules contain peanut oil—contraindicated in peanut allergy 3
- Initial therapy may cause extreme dizziness, drowsiness, blurred vision, or difficulty walking; take at bedtime while standing with water 3
Monitoring Requirements
- Baseline: Endometrial assessment before starting therapy
- Ongoing: Low threshold for endometrial sampling with any unexpected bleeding 2
- Annual: Pelvic exam, breast exam, mammogram 3
- No specific hormone level monitoring is required for symptom management 7
Expected Outcomes
With proper cyclical dosing:
- Endometrial protection: 94% of women avoid hyperplasia (vs 36% with estrogen alone) 3
- Bleeding pattern: Predictable monthly withdrawal bleeding
- Amenorrhea rate: Lower than continuous combined regimens initially, but 73% achieve amenorrhea by 2 years with some intermittent regimens 8
The intermittent approach balances endometrial safety with reduced progestogen exposure, potentially lowering breast cancer risk compared to continuous combined therapy while maintaining effective symptom control 122.