Q.List the three hormones produced in women only during pregnancy. What happens to the levels of estrogen and progesterone during pregnancy ?
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Start your 14-day free trial to unlock the full solution →Three pregnancy-specific hormones are human chorionic gonadotropin (hCG), human placental lactogen (hPL), and relaxin. Estrogen and progesterone levels rise dramatically throughout pregnancy, peaking near term.
The Hormonal Landscape of Pregnancy
Pregnancy triggers a complete endocrine reorganization. While many hormones that exist normally see their levels change, a few are produced exclusively during pregnancy — they serve as chemical signals and support systems for the developing fetus and the mother's adapting body. Understanding which hormones are pregnancy-specific versus which are simply elevated helps clarify the unique physiology of gestation.
Three Pregnancy-Specific Hormones
1. Human Chorionic Gonadotropin (hCG)
This is the earliest marker of pregnancy, secreted by the syncytiotrophoblast cells of the developing placenta within days of implantation. Its primary role is to rescue the corpus luteum from degeneration, ensuring continued progesterone production until the placenta takes over (around week 10–12). hCG is what pregnancy tests detect in urine. Levels peak around 8–10 weeks of gestation, then decline and plateau for the remainder of pregnancy.
2. Human Placental Lactogen (hPL) / Human Chorionic Somatomammotropin (hCS)
Produced by the placenta from about the fifth week onward, hPL has both growth-promoting and metabolic effects. It acts as an insulin antagonist, raising maternal blood glucose to ensure adequate nutrient supply to the fetus. It also stimulates breast development in preparation for lactation. hPL levels rise steadily throughout pregnancy, roughly correlating with placental mass.
3. Relaxin
Secreted initially by the corpus luteum and later by the placenta and decidua, relaxin softens the cervix and relaxes pelvic ligaments to facilitate childbirth. It also inhibits uterine contractions early in pregnancy, helping maintain the pregnancy. Its effects on connective tissue remodeling are crucial for the physical changes of late pregnancy and delivery.
While relaxin is produced in small amounts outside pregnancy (by the corpus luteum during the menstrual cycle), its levels during pregnancy are orders of magnitude higher, making it functionally a pregnancy hormone.
Estrogen and Progesterone During Pregnancy
Both of these steroid hormones, normally cyclic in non-pregnant women, undergo sustained and dramatic elevation throughout the nine months.
Progesterone:
- Initially produced by the corpus luteum (maintained by hCG).
- From weeks 10–12 onward, the placenta becomes the dominant source.
- Levels rise continuously, reaching concentrations 10–20 times higher than peak luteal-phase levels by term. …
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