Noticing your little fella getting a tad smaller? It might be down to that smoking habit you just can't shake.
Speaking to Mirror Online, urologist Marc Laniado says it's not uncommon for smoking to cause both erectile dysfunction and even shrinkage.
"I see erectile dysfunction a great deal," he tells the publication.
"To have a firm erection, you need sufficient blood flow. Smokers have a higher incidence of artherosclerosis in all blood vessels, including those in the penis, which can reduce blood flow.
"The chemicals in smoke may also have an effect on firmness; nicotine causes blood vessels to become narrow. This can be temporary or - eventually - permanent."
"Often they will say: 'My erection is not so good, I don't wake up with an erection in the morning as much as I used to or my penis isn't quite so hard when I'm having sexual relations.'
"But also sometimes people say that their penis is getting shorter as they get older, as smoking stops the blood flowing through the penis, which stops the spontaneous and nightly erections that are needed to stretch the penis and keep it at a good length," he continued.
"So in summary smoking can make your penis appear shorter or in fact become shorter."
Smoking doesn't just affect your Johnson. This is what happens to your face.