MEN'S brains shrink in volume by 8pm every day, a study suggests.

Scientists scanned a 26-year-old's brain 40 times over 30 days and found that after shrinking, the man's brain reset overnight.

Researchers from the University of California, Santa Barbara, say this cycle of growing and shrinking coincides with rising and falling levels of steroid hormones testosterone , cortisol and estradiol.

Study co-author Laura Pritschet - now a postdoctoral scholar in psychiatry at the University of Pennsylvania Perelman School of Medicine - told Live Science : "Males show this 70 per cent decrease from morning to night in steroid hormones.

"You can think of it almost like a pulsating rhythm from morning to night."

Women's hormones also fluctuate daily but it's not as pronounced because th

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