The brain’s role in fertility: Landmark study discovers how the pituitary gland sends pulses to the reproductive organs

A group of scientists from the University of Otago in New Zealand determined how the brain controls fertility, through a landmark study that revealed how the pituitary gland controls the activity of the reproductive organs by sending pulses of hormone.

In their study, they found a group of around 2000 kisspeptin neurons in the hypothalamus that synchronize their activity to create the hormonal pulse. This discovery was essential in better understanding and manipulating fertility.

“Since the discovery of pulsatile hormone secretion over 40 years ago one of the key challenges in this field has been to understand how the brain actually generates these pulses,” said Allan Herbison, one of the authors of the study.

They found that the brain controls fertility by controlling the pituitary gland first, which in turn controls the ovaries in females and testes in males. The brain generates pulses of hormone secretion in the blood about once every hour, which then goes down and tells the ovary or the ovary or the testis what to do.

Women who have polyscystic ovarian syndrome (PCOS) have pulses that occur too rapidly, which often leaves them infertile. PCOS affects around five percent of all sexually mature women. Meanwhile, women with hypothalamic amenorrhea do not generate pulses of hormone or the pulses are too slow, which also leaves them unable to reproduce.

“It turns out that these cells in the brain making kisspeptin are the pulse generator. So having identified them, this means that we can now go in and start manipulating kisspeptin receptors to control the pulses,” Herbison explained.

He explained that even though kisspeptin neurons are present in various places in the brain, those that are located in the hypothalamus, in particular, synchronize their activity at least every hour and send out a signal that generates the pulse of hormone secretion. However, the researchers have yet to understand how these nerve cells synchronize their activity.

“The more detail we can find about the mechanisms involved, the more chance we have of manipulating them to generate or stop synchronization,” Herbison said.

The research was described as a “landmark study” by Stafford Lightman from the University of Bristol, U.K., president of the British Neuroscience Association and a world authority on how pulses of hormones are generated in the bloodstream.

The findings of the study was published in the journal Proceedings of the National Academy of Sciences of the United States of America and was funded by the Health Research Council of New Zealand (HRC).

Fast facts on infertility

Infertility is defined as not being able to reproduce after one year or longer of unprotected sex. Approximately six percent of women in the U.S. aged 15 to 44 years old are infertile, while around 12 percent of women in the same age group have difficulty getting pregnant or carrying a pregnancy to term. The risk of infertility in women increases as they age, smoke, gain extra weight, drink alcohol too much, and get stressed out physically or emotionally. On the other hand, the causes of the increased risk of infertility in men are age, weight, smoking, excessive alcohol intake, marijuana use, frequent exposure of the testes to high temperatures, and exposure to testosterone, radiation, certain medications, and environmental toxins. (Related: Factors behind the growing infertility epidemic affecting millions of Americans.)

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