Pregzilla: Pregnancy, Your Hormones and You
With pregnancy comes a significant change in a number of your hormones. While most of us know this, and understand all too well the impact this can have on our mood and how we feel, many of us don’t really understand what this change in hormones actually means.
A hormone is a signalling or messenger molecule that is produced by your glands and transported in the circulation, targeting specific organs to regulate behaviour and physiology. They are used to influence processes connected to metabolism, lactation, stress, growth, development and reproduction (for example).
What Influences the Production of Reproductive Hormones in Women?
Hormonal secretion mainly occurs in response to biochemical signals. We all know that blood sugar or glucose causes the hormone insulin to be produced. In terms of reproduction:
The female reproductive system has two functions:
- Produce egg cells
- Protect and nourish the offspring until birth and during lactation.
The male reproductive system has one function:
- To produce and deposit sperm.
The four main hormones involved in the production of egg cells are:
- Follicle Stimulating Hormone FSH
- Luteinising Hormone LH
Did you know…
FSH and LH are released from your brain and travel to the ovaries. Once there, FSH stimulates the growth of about 15-20 eggs in each ovary, with each egg being contained in its own shell or follicle. Each follicle gradually matures and becomes dominant over time. FSH also triggers the production of oestrogen by the ovaries. Interestingly however, as the oestrogen level increases it eventually reaches a level that switches off the production of FSH and encourages an increased production of LH. The increased level of LH causes the dominant follicle to release its egg, causing ovulation. The egg is then sucked into the fallopian tube where one lucky sperm may gain entry and fertilise the egg.
The empty follicle remains in the ovary and is now called the corpus luteum. This structure produces oestrogen and progesterone, causing the lining of the uterus to thicken and enable the fertilized egg to embed, resulting in a pregnancy. Oestogen and progesterone are then produced by the placenta, which develops where the egg embeds into the uterus and gradually takes over the hormone production from the corpus luteum (empty follicle).
If fertilization of the egg doesn’t occur, it passes out through the uterus and vagina and as lining of the uterus breaks down it is shed, resulting in a ‘period’.
Significant hormones in Pregnancy and Lactation
- Human chorionic gonadotrophin – HCG
Oestrogen is initially produced by the corpus luteum and then by the placenta. It helps the uterus grow, maintains the lining of the uterus, increases the blood circulation , and helps the baby grow and mature.
Progesterone is also initially produced by the corpus luteum, but by the 10th week of pregnancy, the placenta takes over its production. This hormone has several roles including keeping the uterine muscle relaxed. It also plays a part in the immune system helping the body tolerate the foreign DNA which is part of the newly developing baby.
Levels of both oestrogen and progesterone increase during the first trimester and reach a plateau by the start of the second trimester. This is what often causes mood swings and morning sickness during this first trimester.
Human chorionic gonadotropin – HCG – is produced by what will ultimately become the placenta. HCG helps the ovaries to shut off the production of eggs each month and lets our body know there is a baby developing in the uterus.
Levels of HCG rise 8 days after ovulation and peak at 60-90 days, when they level off for the remainder of pregnancy. During the first 10 weeks of pregnancy HCG levels double every 2 days. This hormone is removed from our body in our urine and it is the measure of this hormone that is the basis of the common urine based pregnancy test.
Relaxin is thought to relax and loosen up the ligaments in our body, particularly the ligaments between the pelvic bones, to prepare the pelvis to relax and expand during delivery. It also causes the cervix to soften during labour and delivery. There is 10x the amount of this hormone in our bodies during pregnancy.
Oxytocin is the hormone that stretches the cervix and is responsible for uterine contractions during labour. After delivery the continued effect of oxytocin causes uterine contractions to decrease the blood supply to the placenta and expel it from the uterus. The levels of Oxytocin gradually increase during labour and peak at delivery.
Oxytocin also plays an important part in breast feeding. Suction to the nipple causes a release of oxytocin, which contracts the muscles in the breast and promotes milk ejection.
Prolactin is a milk producing hormone that increases 10 x during pregnancy. It prepares breast tissue for lactation and the release of milk.
Given the amount of hormonal changes we experience during pregnancy and birth it is hardly surprising that we might feel a little like Pregzilla from time to time.