Regularly enjoy a spliff with a beer or rum? That type of behaviour can cause men to develop a lump in their breasts according to one doctor at King Edward VII Memorial Hospital (KEMH).Daniel Stovell, chief of radiology at the hospital said that it’s common for men who smoke marijuana and drink alcohol excessively.He said a few men come in every year, nervous that they have breast cancer because they’ve developed a lump under one of their nipples.“It is gynaenomastia [pronounced guy-no-koh-mast- tee-ah] which is just a bit of overgrowth of the breast tissue,” Dr Stovell said.Breast cancer is extremely rare in men and when it does occur, it’s almost always in the elderly, he said.And although there are many things that can cause gynaenomastia, most all local cases are a result of cannabis smoking.“With men if you are under 60 or even under 70 it’s very unlikely, but we see guys in their 30s, they smoke marijuana then they feel themselves and say: ‘Oh what’s that lump?’ and they get nervous and they come into us,” he said.The lump is simply extra breast tissue. It is not dangerous and in most cases can be surgically removed.In some studies the lumps disappeared once the men stopped smoking cannabis.A documented case cited in pharmacological reviews by the American Society for Pharmacology and Experimental Therapeutics reads as follows: “A 16-year-old boy who had smoked marijuana since age 11 had short stature, no pubic hair, small testes and penis and low serum testosterone“After stopping smoking, growth resumed and serum testosterone reached the normal range.”It’s believed that THC, the main active chemical compound in cannabis, increases the conversion of the male sex hormone testosterone to the female sex hormone estrogen.The switch stimulates the formation of breast tissue in susceptible men.Another study cited in the same literature said that such biological changes also explain why some cannabis-smoking men reported a decrease in their sex drive and performance.