CD4 and Familial prostate cancer: Because of the possible interactions with the trial β-carotene intervention for T4 and TSH, however, we examined the association between hypothyroid status and risk of prostate cancer stratified by β-carotene supplementation and found no difference (hypothyroid vs. euthyroid: no β-carotene OR = 0.49, 95% CI = 0.23–1.04; β-carotene supplemented OR = 0.46, 95% CI = 0.22–0.96; p for interaction = 0.93).