Crinone is a micronized progesterone gel which is administrated via vaginal route and targeted drug delivery to uterine (first uterine pass effect) with lower serum concentration. This study is to investigate the difference of progesterone concentration in serum and endometrium after administration with crinone and intramuscular progesterone.

The study will be conducted as a single centre, randomized, active controlled study. Recruitment duration will be 6-8 months long. Day 1 of Crinone administration will be the baseline. On Day 7 of Crinone administration endometrial tissue will be taken for P4 test. Last visit will be at 3-5 days after withdraw bleeding.

Inclusion Criteria:

• Perimenopausal women aged <55 years old with amenorrhea>=2 months or reproductive aged women with amenorrhea >= 6months due to premature ovarian failure or other reasons.;
• Serum progesterone level < 1ng/mL
• Endometrial thickness ≥5mm
• No contraindication of progesterone administration;
• Informed consent is signed.

Exclusion Criteria:

• The other kind of progestin was applied 1 month before recruitment;
• Any serious diseases that does not allow to receive the progestin treatment;
• Under any vaginal treatment;
• Any vaginal infectious disease;
• Any other hormone treatment contraindications;
• drug abuse or untreated STD;
• Prior hypersensitivity to Crinone or one of their excipients.
• Pregnant women who indicate hCG positive.