Leptin was once touted as the next miracle weight- loss
drug but when the 'magic' pill failed to deliver, it quickly
faded from the limelight. Recent research, however, has
put the hormone back in the spotlight. Not only does it
stimulate menstruation but it can drive up bone density
levels. So although leptin has been a letdown for the
morbidly obese, it could very well be a boon to the skeletally
skinny.
Dr Christos Mantzoros of Beth Israel
Deaconess Medical Center in Boston headed the study
in the September 2 issue of the New England Journal
of Medicine (NEJM). He believed three categories
of women are likely to benefit from leptin-based drugs.
"The largest group is made up of extremely thin women
who are dealing with problems of infertility; the second
group consists of competitive athletes and dancers whose
thin frames put them at risk for developing osteoporosis
and suffering bone fractures; and the smallest � but
most extreme � group is women who are battling eating
disorders, such as anorexia nervosa," he said.
"Leptin is produced by the body's
fat tissue and is secreted into the bloodstream in proportion
to the amount of energy stored in fat. From there, it
travels to the brain where it communicates exactly how
much energy is available," he explained. Bone formation
and reproduction only takes place if the brain is assured
that the necessary energy is on hand. When body fat
falls drastically, women "stop menstruating and develop
hypothalamic amenorrhea, their ovaries cease to function
and their levels of estrogen and other reproductive
hormones drop dramatically," said Dr Mantzoros. "Amenorrhea
is also associated with loss of bone mass, which can
lead to osteoporosis and fractures."
The researchers recruited 14-competitive
female athletes with diagnoses of hypothalamic amenorrhea
to put some of their theories to a practical test. The
women, who had about 40% less body fat than the norm,
had not menstruated for an average of 5.5 years. Eight
were given a twice-daily preparation of leptin while
the remaining six were simply observed as controls.
The results were dramatic. The women taking leptin not
only began menstruating within weeks, but serum markers
after three months suggested rapidly improving bone
density. None of the controls exhibited any change.
Jeffrey M Friedman, PhD, of Rockefeller
University in NY, first discovered the leptin molecule
in 1994, hailed the work as "a landmark study that will
improve many patients' lives," adding that, "this research
is important in understanding both normal human physiology
as well as the mechanisms leading to several different
disease states."
Nonetheless, there are possible
pitfalls ahead. With its potential for appetite suppression,
giving leptin to anorexic patients may prove tricky.
To fully explore leptin's promising potential, the researchers
are currently designing trials for women with a range
of disorders.
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