The differentiation of the urinogenital system and the appendicular skeleton in vertebrates is under the control of Hox genes. The common control of digit and gonad differentiation raises the possibility that patterns of digit formation may relate to spermatogenesis and hormonal concentrations. This work was concerned with the ratio between the length of the 2nd and 4th digit (2D:4D) in humans. We showed that (i) 2D:4D in right and left hands has a sexually dimorphic pattern; in males mean 2D:4D = 0.98, i.e. the 4th digit tended to be longer than the 2nd and in females mean 2D:4D = 1.00, i.e. the 2nd and 4th digits tended to be of equal length. The dimorphism is present from at least age 2 years and 2D:4D is probably established in utero; (ii) high 2D:4D ratio in right hands was associated with germ cell failure in men (P = 0.04); (iii) sperm number was negatively related to 2D:4D in the right hand (P = 0.004); (iv) in men testosterone concentrations were negatively related to right hand 2D:4D and in women and men LH (right hand), oestrogen (right and left hands) and prolactin (right hand) concentrations were positively correlated with 2D:4D ratio and (v) 2D:4D ratio in right hands remained positively related to luteinizing hormone and oestrogen after controlling for sex, age, height and weight.
Introduction It has been shown in our previous work that breast asymmetry is related to several of the known risk factors for breast cancer, and that patients with diagnosed breast cancer have more breast volume asymmetry, as measured from mammograms, than age-matched healthy women.
Breast cancer is the second most common cancer among women in the world and in developed countries it is the most common. The early identification of women at risk is therefore of great importance and any additional measures which may aid diagnosis, particularly in high risk groups, would be of benefit. Breast volume and breast asymmetry were calculated from mammograms of 250 women with breast cancer and compared with those of 250 age-matched controls. There was evidence that breast cancer patients had more breast asymmetry and larger breasts than age-matched healthy women. The former observation is the first evidence that high breast asymmetry may be a risk factor for breast cancer. Breast asymmetry is likely to be a predictor of, rather than the effect of breast cancer.
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