Progesterone, a crucial steroid hormone in both females and males, though it plays a more dominant role in female reproductive health:
What Is Progesterone?
- Progesterone is a C-21 steroid hormone primarily produced by:
- Corpus luteum (in ovaries)
- Placenta (during pregnancy)
- Adrenal glands (in both sexes)
- Testes (in small amounts in males)
Chemical formula: C₂₁H₃₀O₂
Derived from: Pregnenolone
Acts via: Progesterone receptors (PR-A and PR-B)
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Physiological Functions of Progesterone (Primarily in Females)
Regulation of the Menstrual Cycle
- Secretory phase (post-ovulation): Prepares endometrium for implantation.
- Inhibits uterine contractions to allow embryo attachment.
- Counterbalances estrogen’s proliferative effects.
Support of Pregnancy
- Maintains uterine lining for embryo/fetus.
- Suppresses maternal immune response to prevent fetal rejection.
- Inhibits further ovulation during pregnancy.
- Promotes decidualization (differentiation of endometrial cells).
- Inhibits myometrial contractions, preventing premature labor.
In pregnancy, the placenta becomes the main progesterone source after the first trimester.
Neurological and Mood Effects
- Acts as a neurosteroid in the brain:
- Modulates GABA-A receptors
- Has calming, anti-anxiety effects
- May affect mood and memory
Thermogenic Effect
- Slightly raises basal body temperature after ovulation.
- Basis for tracking ovulation via temperature monitoring.
Bone Health
- Helps regulate bone turnover by modulating osteoblast and osteoclast activity.
- Works synergistically with estrogen to maintain bone density.
Anti-inflammatory & Immunomodulatory Roles
- Regulates local immune responses in the uterus.
- May reduce inflammation and protect tissues during pregnancy.
Functions in Males
- Produced in small amounts in testes and adrenal glands.
- Acts as a precursor to testosterone and other corticosteroids.
- May play a role in sperm maturation and behavior modulation.
Summary Table
Function
Details
Menstrual cycle regulation
Prepares and stabilizes endometrial lining
Pregnancy support
Maintains uterus, prevents contractions
Neurosteroid activity
Anti-anxiety, neuroprotective effects
Thermoregulation
Raises body temp after ovulation
Bone maintenance
Works with estrogen to preserve density
Male role
Precursor hormone, may affect sperm