Hormones and Reproduction

Hormones and Reproduction

A hormone is a chemical substance that is made in one part of the body, then acts like a messenger molecule as it travels to other parts of the body where it helps regulate how cells and organs function. The hormone is secreted into the blood by a gland in response to a signal from the brain. Hormones include the hormones of the thyroid gland (Triiodothyronine (T3) and Thyroxine (T4), insulin, oestrogen, progesterone, prolactin, testosterone, serotonin, cortisol, adrenaline, and the growth hormone. Hormones are an essential aspect of every activity, including the processes of reproduction, growth, metabolism, digestions, and mood control; with some hormones active in more than one physical process, like neurotransmitters.

How Hormones Affect Reproduction

When it comes to reproduction, different hormones regulate the cycles of menstruation, ovulation, and egg production, and your fertility may be affected if these chemicals are out of balance, thus making it more difficult to become pregnant. If this is your story, we urge you to speak to your local practitioner about fertility-related hormones.

LH (Luteinizing Hormone, and sometimes known as Lutropin or Lutrophin) helps in regulating a woman’s menstrual cycle. This is a crucial hormone for promoting a healthy reproductive system. LH is produced in the anterior pituitary gland, and in women this hormone stimulates the production of oestradiol by the ovaries. The ovaries release an egg during ovulation two weeks into the woman’s cycle due to a surge in luteinising hormone. The luteinising hormone stimulates corpus luteum if fertilisation occurs, thus producing progesterone to maintain the pregnancy.A common way to track ovulation is to measure the LH levels. A sudden increase in LH levels will usually last for between 24 and 48 hours, indicating that a mature egg is ready for fertilisation.

GnRH (Gonadotropin-Releasing Hormone; also known as LH-RH, LHRH, and Luteinising Hormone-Releasing Hormone) is produced and secreted by cells in the brain’s hypothalamus. Produced in pulses, GnRH is then carried to the pituitary gland where two more hormones are stimulated. These hormones are Luteinising Hormone and Follicle-Stimulating Hormone, which act on both the ovaries and testes to ensure their reproductive functions. Hormones produced by the ovaries and testes, like progesterone, testosterone, and oestradiol, are controlled by luteinising hormone and follicle-stimulating hormone, which control a male’s sperm production and the maturation and release of an egg during a woman’s menstrual cycle. During different times of the reproductive cycle the pulses of GnRH slow down or speed up.

Oestrogen, produced mainly in the ovaries, is the primary female sex hormone. The term oestrogen also refers to oestrone, oestradiol, and oestriol. Oestrogen levels typically range between 40 and 50 picograms per millilitre. Besides regulating the menstrual cycle, oestrogen promotes the healthy growth of the uterine lining in addition to regulating the frequency of GnRH pulses produced by the hypothalamus. If an egg is fertilised, ovulation during pregnancy is stopped by oestrogen working with progesterone. If an egg is not fertilised, there will be a sharp decrease in oestrogen levels and menstruation begins.

FSH (Follicle-Stimulating Hormone) is produced by the pituitary gland and has the primary role of developing follicles in the ovaries, which is where egg cells mature before ovulation. Follicles produce progesterone and oestrogen and help to maintain a woman’s menstrual cycle. A woman of reproductive age will typically have levels of between 4.7 and 21.5 mIU per ml. An insufficiency of FSH can cause infertility in both men and women.

Progesterone, sometimes known as the ‘pregnancy hormone’, is a natural hormone produced and released by the ovaries. It plays a vitally important role in fertility and pregnancy because it not only helps a woman achieve a pregnancy, it also helps maintain the pregnancy. If an egg is fertilised, progesterone prepares the uterine lining for implantation, and it may even help guide sperm to the egg. Progesterone levels midway through a menstrual cycle will typically increase to between 5 and 20 ng/ml.

The Effects of Hormones on Fertility

The above hormones work together to control the entire course of the reproductive cycle.

  • The pituitary gland receives low-frequency pulses of GnRH, encouraging the production of FSH, thus causing the follicle to develop;
  • Oestrogen levels reach a tipping point as the follicle reaches maturity, so the hypothalamus increases the frequency of GnRH pulses;
  • Ovulation is triggered when the pituitary gland starts producing LH;
  • The follicle now develops into the corpus luteum, producing progesterone, thus letting the uterine lining know to prepare for the egg following fertilisation.

Seeking Help for a Hormone Imbalance

Fertility problems occur when levels of any of the above hormones are too high or too low. Polycystic Ovary Syndrome and a number of other diseases and disorders, like diabetes, can be caused by hormone imbalances. If your general practitioner suspects that a hormone imbalance is affecting your fertility, blood tests will more than likely be recommended. A hormone imbalance is very treatable with injected hormones or drugs; or alternatively, your medical practitioner may choose to treat the underlying problem that’s creating the imbalance. It’s very important that you discuss options with your doctor, including lifestyle changes such as exercise and diet.

Photo Credit:  “Love” (CC BY 2.0) by nromagna

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