Progesterone prepares the uterine lining for implantation and maintains early pregnancy by preventing uterine contractions. It regulates the menstrual cycle, supports breast development for lactation, and raises basal body temperature after ovulation. Produced mainly by the corpus luteum and the placenta during pregnancy, it also influences mood and fluid balance and is made in small amounts by the adrenal glands and testes.

Estrogen and progesterone are female sex hormones with distinct roles. Estrogen (mainly estradiol) drives development of secondary sexual characteristics, follicle growth, and endometrial proliferation in the first half of the cycle. Progesterone is produced after ovulation by the corpus luteum and placenta, stabilizes and prepares the endometrium for implantation, supports early pregnancy, and reduces uterine contractions; both are also made in small amounts by the adrenal glands.

Low progesterone can cause irregular or missed periods, spotting or breakthrough bleeding, a shortened luteal phase, difficulty conceiving or recurrent miscarriage, and heavy or unpredictable menstrual flow. Physical and emotional signs include breast tenderness, bloating, fatigue, sleep disturbances, decreased libido, mood swings, anxiety or depression, and hot flashes. Symptoms vary by person and may overlap with other hormonal issues.

Progesterone helps regulate the menstrual cycle and supports the luteal phase, improving fertility and sustaining early pregnancy when prescribed. It treats irregular or heavy bleeding and is used in hormone‑replacement therapy to protect the uterine lining during estrogen use. Progesterone can reduce menopausal symptoms, alleviate premenstrual syndrome/PMDD, and prevent endometrial hyperplasia in women taking estrogen.

High progesterone levels can cause mood swings, fatigue, drowsiness, dizziness, and breast tenderness. It often leads to bloating, constipation, water retention, and decreased libido; menstrual irregularities or spotting may occur. Progesterone raises body temperature and supports the uterine lining in pregnancy. Very high levels from supplements or disorders can contribute to headaches and worsen depressive symptoms or sedation.

Yes, progesterone can influence weight in some people. It often causes fluid retention, bloating and increased appetite during the luteal phase or when used as hormone therapy, producing modest, usually temporary weight gain. Long-term substantial weight gain is not consistently shown. If weight changes are significant or worrying, discuss alternatives and monitoring with your healthcare provider.