Stockholm: Three American scientists have won the 2017 Nobel Prize in Physiology or Medicine for unravelling secrets of how the body's internal clock or circadian rhythm works -- a discovery that will help doctors understand the mechanism behind sleep patterns, hormone release, blood pressure and body temperature.

Jeffrey C. Hall, Michael Rosbash and Michael W. Young were able to peek inside the human biological clock and elucidate its inner workings, the Nobel Prize committee said in a statement here on Monday.

The winners will share a prize of 825,000 British pounds.

"Their discoveries explain how plants, animals and humans adapt their biological rhythm so that it is synchronised with the Earth's revolutions," said the Nobel Assembly at Sweden's Karolinska Institutet.

The research conducted on fruit flies isolated the "period" gene that controls the normal daily biological rhythm. This gene contained instructions for making a protein called "PER". As levels of "PER" increased, it turned off its own genetic instructions.

"PER" protein was found to accumulate in the cell during the night but degraded during the day. Thus, "PER" protein levels oscillate over a 24-hour cycle, in synchrony with the circadian rhythm.

Chronic misalignments in this clock, as a result of our lifestyle and our external environment, is associated with increased risk for various diseases as well as the temporary disorientation of jet lag that travellers experience while shifting between different time zones.

The scientists also discovered a gene called "timeless" and Young found one called "doubletime", both the genes affecting the stability of "PER".

Hall was born in New York, Rosbash in Kansas City, and they both worked at Brandeis University. In 2002, Hall became associated with the University of Maine.

Michael Young was born in Miami and worked at Rockefeller University in New York.

The Nobel prize in Medicine last year was won by Yoshinori Ohsumi, a Japanese cell biologist, for discovering the process called "autophagy" in which cells destroy and recycle cellular components.