QS Study

Relaxin is a water-soluble hormone which is protein in nature. It is a hormone secreted by the placenta that causes the cervix to dilate and prepares the uterus for the action of oxytocin during labor. It also inhibits contractions of the uterus and may cooperate a function informative the timing of delivery. In the male, it is produced in the prostate and is present in human semen.

Another name: the hormone of pregnancy.

Source: Ovary (corpus rectum), Placenta, Uterus (Possible). Relaxin levels increase after ovulation during the second half of a woman’s menstrual cycle, where it is believed to relax the wall of the uterus and get ready it for pregnancy. If a woman does not conceive, levels drop until the next cycle.

Fig: Hormonal regulation of the menstrual cycles.


(i) Relaxation of some pelvic structures. (symphysis pubis, pelvic joint)

(ii) Dilation of the cervix during pregnancy helps in growth and expulsion during parturition.

(iii) This hormone also stops contractions as the tiny baby grows to prevent early delivery.

(iv) It has also been found to reduce blood pressure by relaxing the blood vessels.

(v) Relaxin promotes the development of the nipples and mammary glands in pregnant mammals.

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