The hormone dependency of the ovaries and the functional similarity of THRs and estrogen- (ER) and progesterone receptors (PR; both act in the nucleus as transcription factors) lead to the hypothesis that THRs may be a prognostic marker in ovarian cancer patients as demonstrated recently for breast cancer patients (Li et al. 2002; Rasmusson et al. 1987; Turken et al. 2003; Ditsch et al. 2013). The gene discussed is ESR1; the disease is ovarian carcinoma.