Injections of a hormone that is normally a factor in obesity can help to kick-start the ailing reproductive systems of overly thin women, new research has shown.
Leptin appears to regenerate the fertility cycle in female athletes who had become so lean that their periods stopped.
Leptin has been long known to regulate appetite and weight by informing the brain how much energy is available in the body. It is also thought to play a key role in determining obesity levels.
Women who are particularly thin, such as athletes with rigorous training programmes or women on very restrictive diets, produce less leptin. In extreme cases, the woman's body enters a state of negative energy balance and her reproductive system shuts down to prevent a pregnancy and conserve energy, a condition called hypothalamic amenorrhoea or dysfunction.
But research reported last week in the New England Journal of Medicine suggests that there may be a solution. Scientists at the Beth Israel Deaconess Medical Centre in Boston carried out tests to see whether giving women leptin would reverse the condition.
Five out of eight female athletes, whose periods had stopped five or more years ago as a consequence of exercise regimes, began to menstruate again after receiving leptin injections twice a day for three months. Three also started to ovulate. In comparison, six female athletes given no treatment at all showed no improvement.
The team said the injections might also prevent bone loss and help treat anorexia nervosa, sufferers of which also risk bone loss owing to the resultant lack of female hormones, which can lead to osteoporosis.
Dr Chris Mantzoros, who led the study, said the benefits of leptin were three-fold. 'This could eventually prove beneficial to patients with anorexia, competing athletes with brittle bones, and last but not least, to approximately 30 per cent of women whose fertility problems can be attributed to hypothalamic dysfunction.'
The researchers plan to carry out longer studies to determine the safety, dose and efficacy of leptin treatment.
Dr Richard Fleming, an expert in reproductive endocrinology at Glasgow Royal Infirmary and a member of the British Fertility Society, said: 'The results are interesting and important. These data imply that leptin is the key, and will perform the trick even if the energy stores are not there.'
But he warned that great care would have to be taken with respect to pregnancy in women with subnormal energy stores, because pregnancy would be high risk for both the mothers and the children.
