Thyroid Hormones and Morphological Features of Primary Breast Cancer

Many experimental studies have suggested the importance of thyroid hormones in breast cancer (BC) morphogenesis. The aim of this study was to evaluate the association of thyroid hormone levels in serum of patients with primary BC with morphological presentations of the disease in pathological specimens and prognosis.

We measured the serum levels of thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxine (FT4), along with serum thymidine kinase 1 activity and examined their relation to pathological features and prognosis of 158 patients with primary BC.

We found a significant positive association of serum FT3 level with the presence of carcinoma in situ component (CIS) (p=0.032) and its size (p=0.047), with the presence (p=0.022) and the number of multifocal/multicentric tumors (MMTs) (p=0.002), as well as with increased proliferative activity in terms of serum thymidine kinase 1 (p=0.002). Moreover, we report that each 1.0 unit rise of FT3/FT4 ratio×10 was associated with an odds ratio of 1.77 (95% confidence interval=1.17-3.30, p=0.007), 1.97 (95% confidence interval=1.17-2.67, p=0.010) and 1.56 (95% confidence interval=1.02-2.37, p=0.039) for the detection of patients with CIS, MMTs and lymphovascular invasion, respectively, after adjusting for age. We did not find statistically significant associations of serum TSH level with breast cancer`s parameters. A Cox regression survival analysis identified serum FT3 level >5.95 pmol/l as a risk factor for BC recurrence (relative risk=2.65, p=0.017), a finding that retained significance in a multivariate model (relative risk=2.52, p=0.027).

The FT3/FT4 ratio is a valuable parameter predicting the presence of CIS, MMTs and lymphovascular invasion in pathological specimens. An elevated serum FT3 level is associated with the presence of CIS, MMTs, increased proliferative activity and poor prognosis.