Hormonal Manipulation in Sport, Health and Agriculture

Hormones as chemical messengers

A hormone is a chemical messenger made by an endocrine gland, carried in the blood and acting on target cells that have the matching receptors. Hormonal control is slower than nervous control but lasts longer. Because hormones are carried by the blood, a synthetic copy given to a person or animal acts exactly as the natural hormone does.

Most hormone control works by negative feedback: a rise in the hormone's effect switches off its own release. This idea explains almost everything on this page.

Hormones in health

Hormones are used as medicines in two ways: to replace a missing hormone, or to change a natural process.

Insulin. In type 1 diabetes the immune system destroys the insulin-producing beta cells in the pancreas. Without insulin, cells cannot take up glucose and blood glucose stays dangerously high. People inject insulin, which lowers blood glucose by helping cells absorb glucose and by promoting its storage as glycogen in the liver and muscle. Insulin is a protein, so it would be digested if swallowed: it must be injected (or delivered by a pump).

Hormone replacement therapy (HRT). At the menopause the ovaries stop responding to FSH and LH, so oestrogen and progesterone levels fall. This causes hot flushes, mood changes, vaginal dryness and loss of bone density. HRT supplies oestrogen (usually with progesterone if the woman still has a uterus). A benefit is relief of symptoms and slower bone loss (reduced risk of osteoporosis). A risk is a small increased risk of blood clots, breast cancer or stroke with some types of HRT, so each woman discusses it with her GP.

Human growth hormone (hGH). Made by the pituitary, it is given to children with a deficiency who would otherwise be very short. This is a replacement therapy.

Hormones in sport

The World Anti-Doping Agency (WADA) bans substances that enhance performance, harm health or go against the spirit of sport. In Ireland, Sport Ireland Anti-Doping tests athletes in the GAA, rugby, athletics and cycling, often without notice.

Anabolic steroids and negative feedback

Anabolic steroids resemble testosterone. A high level of steroid in the blood is detected by the hypothalamus and pituitary, so the pituitary secretes less FSH and LH. With little LH, the testes make less natural testosterone; with little FSH, sperm production falls. Without stimulation the testes shrink.

EPO

EPO is made by the kidney when oxygen levels in the blood are low. It stimulates red bone marrow to make more red blood cells. An athlete using synthetic EPO has more haemoglobin, so more oxygen reaches muscles, allowing more aerobic respiration and delaying fatigue. The risk is that more red cells make the blood more viscous (thicker), so it flows slowly and clots may form, leading to stroke or heart attack.

Why testing is difficult

Synthetic EPO and steroids are chemically almost identical to natural ones, so tests must distinguish tiny differences or detect abnormal ratios (for example testosterone to its relatives). Hormone levels vary naturally and are cleared quickly, and athletes may stop use before a competition. Testing is still done regularly because it deters cheating, protects health and keeps competition fair; out-of-competition tests and stored samples that can be re-analysed make cheating risky.

Hormones in agriculture

Farmers can use hormones to increase output or to control breeding.

• Bovine somatotropin (BST), a growth hormone given to dairy cows in some countries, raises milk yield, so the farmer sells more milk per cow.

• Growth promoters (anabolic steroids) in beef cattle increase muscle growth and feed conversion, giving more meat from the same feed. They act on muscle cells to stimulate protein synthesis, so more amino acids are built into muscle protein and the animal puts on lean tissue faster.

• Synchronisation of oestrus: all cows in a group come into heat together, so they can be inseminated on the same days and calve in a tight block.

Synchronising a dairy herd

A device releasing progesterone is placed in the vagina for about a week. The high progesterone level exerts negative feedback on the pituitary, preventing FSH and LH surges, so no cow ovulates. An injection of prostaglandin is given towards the end of the treatment, usually on the day the device is removed. It causes any corpus luteum to regress (break down), so natural progesterone production stops. When the device is removed, progesterone falls, the pituitary releases FSH and LH, follicles develop and all cows return to heat at the same time.

Evaluating the practices

Without hormones, Irish farmers can improve productivity by selective breeding for high-yield or fertile animals, better grassland management (grazing on high-quality grass), improved feed and mineral supplements, good animal health and herd records.

Producing hormones safely: recombinant DNA

Insulin and hGH used to be extracted from animals or human cadavers. Cadaver pituitaries could carry infectious agents such as prions (causing Creutzfeldt–Jakob disease), the supply was tiny, and quality varied.

Today the human gene is cut out using restriction enzymes and inserted into a plasmid, a small ring of DNA, which is joined by DNA ligase. This recombinant plasmid is put into bacteria (or yeast), which then make the human protein as they divide in a fermenter. The hormone is purified. Benefits: large amounts, identical to human hormone, no risk of cadaver-borne disease.

Ethics of enhancement

Using hGH to treat a deficiency restores normal health. Using it to win races or to make a healthy child taller is enhancement. Arguments against: unfair advantage, health risks, pressure on young athletes, and medicalising normal variation in height. Arguments for: personal autonomy, and the claim that all training and diet already enhance performance. Strong answers weigh both sides and reach a reasoned conclusion.

Back to the start: the cyclist is banned because the hormone is used to gain an unfair advantage at risk to her health; the child's insulin replaces a missing hormone; the farmer's device uses negative feedback to control breeding for profit, raising welfare and trade questions.

Summary

• Hormones are chemical messengers carried in the blood; most are controlled by negative feedback.

• Insulin (from the pancreas) lowers blood glucose and is injected in type 1 diabetes; HRT supplies oestrogen and progesterone after menopause.

• Anabolic steroids mimic testosterone and cut FSH and LH, so testes shrink and sperm production falls; EPO raises red cell numbers, boosting endurance but thickening blood.

• Agricultural uses: BST, growth promoters, and progesterone devices with prostaglandin to synchronise oestrus; the EU bans growth promoters.

• Recombinant DNA makes hormones such as insulin and hGH safely; enhancement raises ethical issues.