Leptin & Reproduction

Discovered in 1994, the hormone leptin first gained attention as an indicator of the body's energy stores. Your fat cells are the primary producers of leptin; the blood level of the hormone correlates to the amount of fat in your body. In addition to suppressing hunger, leptin affects your reproductive system processes, including puberty, pregnancy and menstruation or sperm production.

The Energy-Reproduction Link

Survival is a primal drive for all living beings. Food is one of the requisites for survival because it provides the energy-generating fuel to support your body functions. Fat tissue is the energy reservoir for your body; your leptin level indicates how full your reservoir is. Unlike your brain, heart, lungs and liver, your reproductive system is not essential for survival. When fat reserves are low, your body may divert energy away from your reproductive system to increase the amount available to support your essential organs. Leptin is the link between your energy reservoir and reproductive system. Your brain and reproductive organs have receptors that sense the leptin level in your blood. If your leptin level is low because of a reduced amount of body fat, your reproductive system functions may be impaired until your nutritional status improves.

Puberty

The timing of female puberty is influenced by hormonal, nervous system and genetic factors. A sufficient fat reserve, reflected by an adequate leptin level, is one of the requisites for the onset of puberty. Additionally, elevated leptin levels associated with childhood obesity may trigger the early onset of puberty in girls, reports Dr. Paul Kaplowitz in a February 2008 article published in the journal "Pediatrics." The possible role of leptin in the onset of male puberty is unclear.

Fertility

The amount of fat in your body may affect your fertility through the effects of leptin. Nutritionist Judith Brown, Ph.D., and coauthors note in "Nutrition Through the Life Cycle" that a 10 to 15 percent reduction in body weight causes a dramatic decrease in your blood leptin level, which may temporarily disrupt ovulation and menstruation or reduced sperm production. Being underweight with low levels of body fat and leptin also commonly leads to impaired fertility among men and women. This situation often develops with ongoing rigorous physical activity or an eating disorder. Replenishing your body fat reservoir usually restores fertility.
High leptin levels caused by overweight and obesity may also adversely affect your fertility by disrupting the balance of sex hormones in your body. Weight loss is an important component of therapy for obesity-related fertility problems.

Pregnancy

During pregnancy, the fat cells of the mother and baby and the placenta produce leptin. Blood leptin levels remain high throughout pregnancy, stimulating the baby's bone and lung development and supporting the mother's body in sustaining the pregnancy. Reduced leptin levels during pregnancy may impede the baby's growth. An abnormally high leptin level may lead to pregnancy-induced hypertension, or preeclampsia, which may endanger the mother and baby.