When the T4 and TSH measurements were combined to define men as being in a hypothyroid, euthyroid or hyperthyroid hormonal state, we found that men who were hypothyroid (i.e., TSH≥3.0 μIU/mL and T4<4.6 μg/dL) had a statistically significantly reduced risk of overall prostate cancer compared to euthyroid men (Table 4). This evidence concerns the gene CD4 and prostate cancer.