Why does it happen?

There are thought to be several reasons why hypospadias occurs. In some cases it is passed down from a male relative (often the father) to the son, so it is classified as hereditary. In other families, an uncle or a grandfather may have hypospadias. However, this family occurrence is seldom known or openly discussed so the genetic inheritance cannot be easily established.

A second, but not very common, cause appears to be the side-effects of drugs (that includes illegal drugs, and medicines or pills) which the mother has taken while she is pregnant or trying to become pregnant. Drugs that have been linked to a higher occurrence of hypospadias include:

  • The anti-epilepsy drugs, Valproic acid and Phenytoin;
  • the hormone Progesterone, often given to mothers as part of IVF treatment;
  • DES (Diethylstilbestrol) prescribed up until the 1970s to prevent miscarriage
  • Clomiphene, a drug used to induce ovulation during IVF treatment;
  • Loratidine, an anti-allergy drug, though the evidence now seems to suggest that Loratidine is not a risk factor in hypospadias.

Also, the frequency of hypospadias is higher in boys born to mothers addicted to cocaine.

There may of course be other drugs which can affect the development of a boy’s penis while he is in his mother’s uterus, but which have not yet been shown to cause hypospadias.

A third cause of hypospadias may be the increase in levels of man-made chemical pollutants in the world around us. This increase may also explain why hypospadias is becoming more common in our society. Some chemicals like pesticides, fungicides and industrial pollutants are suspected of causing an increased level of hypospadias as well as other birth defects

A fourth cause of hypospadias is hormonal. If either mother or children are exposed to high levels of female hormones, or if there is something wrong with the baby’s own hormone system, the baby may develop hypospadias. Doctors have known for a long time that a small proportion of cases of hypospadias are caused by a male child’s penis not developing properly in response to the testosterone produced by his testicles during pregnancy.

There are probably other causes of hypospadias, but at the moment we cannot always be sure what has caused a particular case.