Both genes and the environment contribute to PCOS. Obesity, exacerbated
by poor dietary choices and physical inactivity, worsens PCOS in
susceptible individuals. The role of other environmental modifiers such
as infectious agents or toxins are speculative. Phenotype confusion has
characterized genetic studies of PCOS. Although several loci have been
proposed as PCOS genes including CYP11A, the insulin gene, the
follistatin gene, and a region near the insulin receptor, the evidence
supporting linkage is not overwhelming. The strongest case can be made
for the region near the insulin receptor gene (but not involving this
gene), as it has been identified in two separate studies, and perhaps
most importantly has not yet been refuted by larger studies. However,
the responsible gene at chromosome 19p13.3 remains to be identified. To
date, no gene has been identified that causes or contributes
substantially to the development of a PCOS phenotype
