New research shows that there is a genetic connection between metabolic functions and reproductive functions in both men and women.

The study, conducted by an international team of scientists has found genetic marker that influences protein called sex hormone-binding globulin (SHBG) in the blood stream. This protein is responsible for regulation of estrogen and testosterone in human blood stream.

Sex hormone-binding globulin (SHBG) is a protein mainly secreted by the liver that binds to sex hormones in the body and transports them in the blood stream, researchers said. SHBG influences the sexual characteristics of men and women.

SHBG has also been linked to various diseases like diabetes type-2 and certain types of cancers like breast and prostate cancer that are dependent on sex-hormones.

For the study, researchers analyzed genomes 21,791 men and women to see what genes are responsible for SHBG functions. They identified 12 single-nucleotide polymorphisms (SNPs) that were bound to the circulating SHBG in the blood stream.

Researchers validated their results by studying genomes of another 7,046 men and women. They found that the genetic variations for this protein occurred more in men than in women.

They also found that the genetic markers for SHBG were present near genes that influence fat, carbohydrate metabolism and even diabetes type 2 in humans According to researchers, the fact that these genes (metabolism and reproduction) are close together may explain why there is a difference in the onset of certain diseases in men and women.

"These findings underscore the connection between the reproductive system and metabolism in both men and women, and may help explain sex differences observed in some metabolic diseases, particularly type 2 diabetes," said Dr. Andrea D. Coviello, assistant professor of medicine at BUSM, endocrinologist at Boston Medical Center and one of the lead authors of the study, in a press release.

Single-nucleotide polymorphisms (pronounced as "snips") are variations that occur in DNA when a single nucleotide in the genomic sequence is altered. SNPs are studied because scientists believe that these variations will help them find multiple genes associated with cancer, diabetes, heart disease among many others.

The study is published in the journal PLoS ONE Genetics.