"There is evidence that certain hormones, or growth factors such as insulin, act to stimulate cancer cell growth, " he says.

CNN: Obese may be less likely to survive pancreatic cancer

Dr Wehr suspects that the effect may have to do with a surge, during the wee hours, of certain hormones associated with the thyroid.

ECONOMIST: People, like all living things, are four dimensional

Dr. Pressman is currently researching how smiling affects certain stress hormones, such as cortisol, and oxytocin, which is sometimes called the trust hormone.

WSJ: Stress-Busting Smiles

Prostate cells, including cancerous ones, are sensitive to levels of certain male hormones, and can be rendered far less active if levels are reduced.

BBC: Prostate cancer

The technique is based on classifying patients by the genetic make-up of certain of their hormones that are involved in the immune response.

BBC: Surgery