Many of the things that can go wrong with the reproductive system are specific either to men or to women, and so there is a section on each sex. But some factors affect both sexes in a broadly similar manner, and so it will save space to consider them together.
Hormonal causes of infertility include:
- CAH (Congenital Adrenal Hypoplasia)
Physical damage to the hypothalamus or pituitary
Low fat reserves, usually linked to eating disorders
Hormones are the body’s long-term communication system. They are chemicals which circulate through the body often, but not exclusively, through the bloodstream and trigger responses in cells. In contrast to the nervous system (which shoots messages across the body in fractions of a second, to be acted on and then instantly forgotten), hormones act over a period of minutes, hours, or days.
The patterns of rising and falling levels of hormones determine many of the cycles that our bodies follow not least those of the reproductive system. Estrogen and testosterone, the female and male sex hormones*, are probably the best-known hormones in the body. The supporting cast – follicle-stimulating hormone, gonadotropin-releasing hormone, and the like don’t get as much attention, but our reproductive systems depend heavily on them and their interactions with each other.
It’s no surprise, then, that when this chemical soup of hormones has too much or too little of some ingredient, our bodies can fail to do what we expect them to. The relevant hormones are produced in the genitals, and in two small regions of the brain called the hypothalamus and the pituitary. Disruption to these two regions can cause hormonal problems which lead to sub-fertility.
What would cause this disruption? Obviously, physical damage such as a head injury could do it. More commonly, the hypothalamus is affected indirectly. Drugs can do it the contraceptive pill works by reducing the amount that the hypothalamus produces Gonadotropin Releasing Hormone. The hypothalamus is also affected by an unhealthy lifestyle. Extreme loss of fat deposits, commonly caused by anorexia, bulimia, or excessive exercise, can also cause the disruption.
Another mechanism is through a condition called hyperprolactinaemia, where too much of the hormone prolactin is produced in the body. Prolactin usually works on the breasts, encouraging them to produce more milk. But it also has an effect on the hypothalamus, reducing the amount of other hormones that it produces. So having too much prolactin in your body reduces the amount of Gonadotropin-releasing Hormone, which can cause infertility.
Yet another imbalance can come in the form of problems with the adrenal glands. As the name suggests, these glands produce adrenaline, but they also produce other hormones called cortisol and aldosterone, and androgens. The androgens are male sex hormones, and so they affect the reproductive system. In a genetic condition called Congenital Adrenal Hypoplasia (CAH), these androgens are produced at too high a level.
The mechanism leading to the over-production is a typical case where the body notices a problem, corrects it, and in doing so causes a second problem. Let’s look at it in stages:
- 1.The initial problem is a genetic defect within the adrenal glands, which causes under-production of cortisol and aldosterone.
2.The body’s response is to create a hormone called ACTH, which tells the adrenal glands to produce more hormones. However, this doesn’t tell it to produce more of one particular hormone, just to generally step up production.
3.The side effect is that the adrenal glands start to produce more hormones not just more cortisol and aldosterone (the desired response), but also more androgens (the undesired side-effect)
4.The result is a higher circulation of androgens in the body. These changes begin before birth (remember that CAH is genetic), and lead to abnormal growth of the genitals in girls.
CAH as a full condition affects only one in 15,000 people, although it has been claimed that a milder form affects one in every hundred of us.
There are many other rare genetic conditions which cause infertility, through an imbalance of some sex-related hormone. They end up separated into exotic-sounding syndromes Kallman Syndrome, Prader-Willi Syndrome, Bardet-Biedl Syndrome depending on the underlying causes.
These syndromes are mostly genetic, and usually they affect more than just the reproductive system. Prader-Willi Syndrome, for example, is caused by a problem with one particular gene, and leads to obesity, and small hands and feet. If you suffer from one of these conditions, it’s unlikely that fertility problems will be the first that you hear of it. They’re also very rare, each only affecting one person in many thousands.