Are thyroid and sex hormone ratios predictive of breast cancer risk? a preliminary study among a cohort of sri lankan breast cancer patients

Purpose: The association of thyroid related diseases and sex hormones with breast cancer (BC) is reported with inconclusive results. The study was designed to analyse the thyroid/sex hormone ratios of BC patients. Material and Methods: TSH, T3, T4, estrogen, progesterone and testosterone concentrations of newly diagnosed breast cancer patients (n=155) aged 30 to 75 years and age-matched normal controls (n=75) were analyzed. Thyroid: sex hormone ratios were calculated. Data on history of thyroid related diseases were collected. Results: History of thyroid related diseases was significantly higher (p<0.05) in breast cancer patients compared to controls. Among the remaining, subclinical hyperthyroidism was found in 14%, but only 7% in healthy women. Significantly higher (p<0.05) mean T3 and T4 values and lower TSH levels were observed in patients with breast cancer when compared to healthy. Serum testosterone was significantly low among BC patients. Considering the thyroid to sex hormones ratios among postmenopausal women, T3/testosterone, T4/testosterone, T3/estrogen, T4/ estrogen, ratios were significantly different compared to healthy and the highest significance was found with T3/testosterone. Cutoff values studied from receiver operative characteristic curves indicated that a woman having T3/testosterone above 7.47 showed 12.5 times odds (p=0.000) of being diagnosed with BC. Conclusion: The present study concludes that the incidence of thyroid related diseases is higher among Sri Lankan BC patients and elevation of T3/testosterone ratio is indicative of BC.