Another group of patients in this category are those that had radiation for cancer. This includes radiation to the neck or chest for Hodgkins' Disease, Non-Hodgkins' Lymphoma, and even breast cancer. Like the group of young people above getting radiation for benign disease, those getting hyperparathyroidism due to radiation to the neck get the parathyroid tumor about 17 years later on average (range 9 years to 40 years). The incidence of multiple tumors is about 16%, and is usually on the side of the radiation (if the radiation was on one side of the neck).
There are many underlying physical and psychological causes of erectile dysfunction. Reduced blood flow to the penis and nerve damage are the most common physical ED causes. Underlying conditions associated with erectile dysfunction include the following:
Hulshoff Pol et al. (2006) studied the gross brain volume of 8 male-to-female transsexuals and in 6 female-to-male transsexuals undergoing hormone treatment. They found that hormones changed the sizes of the hypothalamus in a gender consistent manner: treatment with male hormones shifted the hypothalamus towards the male direction in the same way as in male controls, and treatment with female hormones shifted the hypothalamus towards the female direction in the same way as female controls. They concluded: "The findings suggest that, throughout life, gonadal hormones remain essential for maintaining aspects of sex-specific differences in the human brain."