Reproductive hormones are responsible for pregnancy, puberty, menstruation, menopause, sex drive, sperm production, labour and breastfeeding/lactation.  These hormones are produced in the ovaries (in females) and testes (in males) as well as the pituitary gland and the placenta.

Anti-mullerian (AMH)

This hormone is produced in the granulosa cells in a woman’s ovarian follicles and is a marker for the number of available oocytes, which are cells that participate in the formation of an egg.  AMH does not change during the menstrual cycle and can be tested at any time of the cycle. (1)

Gonadotropin-Releasing Hormone (GnRH)

GnRH hormone is produced and secreted by specialised nerve cells in the hypothalamus of the brain.  GnRH is carried from the brain to the pituitary gland, where it stimulates the production of follicle stimulating hormone (FSH) and luteinising hormone (LH), which allow the testes and ovaries to act on their respective reproductive functions.

Follicle-stimulating hormone (FSH)

FSH is produced and released by your pituitary gland.  FSH plays a role in sexual development and reproduction.  This hormone stimulates the maturation of the Graafian follicles in the ovary in women and in men, it stimulates spermatogenesis in the testicles.  In the second and third trimesters of pregnancy, the fetus’ pituitary gland releases FSH and luteinizing hormone (LH).  During puberty, FSH and LH work together so that the testes produce testosterone in boys and the ovaries produce oestrogen in girls. (2)

Human placental lactogen (hPL)

hPL is a hormone produced by the placenta when a woman is pregnant.  hPL can alter the metabolism of women during pregnancy allowing nutrients to reach the fetus.  It also helps with insulin sensitivity and prepares the body for breastfeeding. hPL is also called human chorionic somatomammotropin (HCS).  A low level of hPL might mean risk of miscarriage, pre-eclampsia or problems within the placenta or fetal growth.

Human chorionic gonadotropin (HcG)

HcG is a hormone made by the placenta during pregnancy.  HcG levels begin to rise after conception and it is this hormone that is detected in blood or urine to confirm a pregnancy.  It stops increasing at around 10 weeks gestation.  HcG also triggers the body to create more progesterone and estrogen.  HcG tells the body to stop menstruating and thickens the uterine lining to support a growing embryo. (3)

Inhibin

This hormone inhibits the secretion of the FSH by the anterior pituitary gland. It is secreted by the granulosa cells in the ovaries.  This creates a typical negative feedback loop between inhibin and FSH to stimulate the formation of granulosa cells which produce estrogen and progesterone.  In the testes, small amounts of inhibin hormone are produced by the sertoli cells.

Luteinizing hormone (LH)

The pituitary gland releases LH which causes changes to occur in the ovaries and testes.  LH stimulates the ovaries to maintain your menstrual cycle and support pregnancy.  A high surge in LH causes release of an egg in around the middle of the menstrual cycle, called ovulation and most likely when a woman can fall pregnant.  LH also causes progesterone increase during the third and fourth week of a cycle to support a pregnancy.  As you age and go through menopause, your LH levels will increase as your levels of estrogen and progesterone decrease.

In males LH stimulates your testes to make testosterone and LH levels remain fairly stable in men after puberty.

Prolactin (PRL)

PRL is a hormone that’s responsible for lactation, certain breast tissue development and other bodily processes.  Prolactin levels are normally low in males, non-lactating and non-pregnant women. They’re normally elevated in women who are pregnant or breastfeeding.  Prolactin is made and released by the pituitary gland.

During pregnancy, prolactin, estrogen and progesterone stimulate breast tissue development and milk production.  Prolactin promotes the growth of breast tissue called mammary alveoli, where the production of milk occurs.  Prolactin also stimulates the alveolar cells to create milk components of lactose, casein and lipids.

Relaxin

In women, Relaxin is secreted into the circulation by the corpus luteum in the ovary.  Relaxin levels in the circulation rise after ovulation, during the second half of the menstrual cycle.  At this stage it is thought to relax the wall of the uterus by inhibiting contractions, and it also prepares the lining of the uterus for pregnancy.  If pregnancy does not occur, Relaxin levels drop again.  During pregnancy it is released from the placenta, the membranes which surround the foetus, and the lining of the uterus.  Levels are at their highest in the first trimester.  Towards the end of pregnancy Relaxin promotes rupture of the membranes surrounding the fetus and the growth, opening and softening of the cervix and vagina to aid the process of childbirth.

In men, Relaxin is secreted from the prostate gland and can be detected in the semen, but is not generally found in the blood circulation.  (4)

Testosterone

In men, the testicles primarily make testosterone.  Women’s ovaries also make testosterone in smaller amounts.  The production of testosterone starts to increase significantly during puberty where it is essential for growth of muscle, bone and hair mass.  It begins to dip after age 30 or so.  Testosterone is most often associated with sex drive and plays a vital role in sperm production.  A man’s testosterone levels can also affect his mood, storage of fat in the body, and red blood cell production.

Progesterone

Progesterone participates in the female reproductive system, menstrual cycle, promotes gestation in pregnancy and the formation of the embryo.  The main function of progesterone is to prepare the endometrium for a fertilized egg to implant and grow.  Ovulation occurs around the middle of a woman’s menstrual cycle.  The corpus luteum forms from the empty egg follicle and begins producing progesterone.  It works by thickening your uterine lining and creating a good environment for a fertilized egg to implant.  If a pregnancy doesn’t occur, the endometrium sheds (menstrual period).  If conception occurs, progesterone increases to support the pregnancy.  Low levels of progesterone following implantation, can often result in pregnancy loss.  (5)

Estrone (E1)

Estrone is one of three Estrogen hormones, often the weakest type and continues to be made after menopause.  Estrone forms in the adrenal glands and adipose tissue.  The ovaries also produce estrone.  It can convert to estradiol when your body needs a stronger type of estrogen.  In people who continue to experience fatigue, hot flashes or low sex drive after menopause, low estrone could be the cause.  High estrone levels may increase the growth of breast and uterine growths. (6)

Estradiol (E2)

Estradiol is the main hormone present during a woman’s reproductive years.  The ovaries produce estradiol in varying amounts depending on where a person is in their menstrual cycle and reproductive timeline.  Some smaller amounts of estradiol are produced in the adrenal glands, fat cells, breasts, and brain via cholesterol.  Estrodiol levels begin to increase during puberty, rise and fall within the menstrual cycle, and decline as the person ages. (7)

Estriol (E3)

Estriol is the third hormone in the estrogen group.  Normally, levels of Estriol in the body are very low, but during pregnancy, it is made in much higher amounts by the placenta.  Estriol levels increase throughout pregnancy and are highest just before birth.

Men also produce small amounts of estrogen.

References

1. Anti mullerian Hormone (AMH) test & ovarian reserve. (n.d.). IVF Australia. https://www.ivf.com.au/planning-for-pregnancy/female-fertility/ovarian-reserve-amh-test
2. Professional, C. C. M. (n.d.-a). Follicle-Stimulating Hormone (FSH). Cleveland Clinic. https://my.clevelandclinic.org/health/articles/24638-follicle-stimulating-hormone-fsh#What%20Is%20Follicle-Stimulating%20Hormone%20(FSH)?
3. Professional, C. C. M. (n.d.-c). Human chorionic gonadotropin. Cleveland Clinic. https://my.clevelandclinic.org/health/articles/22489-human-chorionic-gonadotropin
4. Relaxin | You and Your Hormones from the Society for Endocrinology. (n.d.). https://www.yourhormones.info/hormones/relaxin/
5. Professional, C. C. M. (n.d.-i). Progesterone. Cleveland Clinic. https://my.clevelandclinic.org/health/body/24562-progesterone
6. Professional, C. C. M. (n.d.-c). Estrone. Cleveland Clinic. https://my.clevelandclinic.org/health/body/22398-estrone
7. Mutchler, C. (2023, August 31). The difference between estradiol and estrogen. Verywell Health. https://www.verywellhealth.com/estradiol-vs-estrogen-why-hormone-levels-matter-7566712