A drug originally designed to treat osteoporosis could cure hair loss in men and women, researchers from the University of Manchester have found.

It had "a dramatic stimulatory effect on human hair follicles donated by patients," the university said in a statement.

Scientists initially studied an old immunosuppressive drug called CsA, which has a side-effect of hair growth.

They found it reduced the expression of protein SFRP1, which inhibits the growth of many tissues, including hair follicles.

But the drug has severe side-effects.

Lead researcher Dr Nathan Hawkshaw did some "detective work" and found an osteoporosis drug, WAY-316606, targets the same mechanism as CsA — without its side-effects.

He treated hair follicles with WAY-316606, and found external application of the compound to a balding human scalp "may promote hair growth to the same magnitude as CsA or even better".

"The fact this new agent, which had never been considered in a hair-loss context, promotes human hair growth is exciting because of its translational potential," Dr Hawkshaw said.

"It could one day make a real difference to people who suffer from hair loss."

There are currently two drugs available to treat balding — minoxidil (for men and women) and finasteride (for men) — but both have side-effects and are not always effective.

Dr Hawkshaw said clinical trials will now be required, to find if the new potential treatment is effective and safe in patients.