Edao, AbebeAlem, MekdesHailu, Habteyes (PhD)Meles, Mehari2025-08-272025-08-272025https://etd.aau.edu.et/handle/123456789/7155Background: Breast cancer (BC) is the most common cancer in women, with high global mortality. Vitamin D deficiency and thyroid dysfunction may influence BC through hormonal regulation and immune modulation. Thyroid hormones affect cell metabolism and proliferation, while vitamin D has anti-proliferative effects on breast tissue. Thyroid dysfunction can alter estrogen metabolism, impacting BC risk. However, data on serum vitamin D and thyroid hormone levels in Ethiopian BC patients are limited. This study aims to assess these levels in newly diagnosed female BC patients. Methods: A Facility-based comparative cross-sectional study was conducted from January to March 2024 in Tikur Anbessa Specialty Hospital. A convenient sampling method was employed to recruit 69 females newly diagnosed with breast cancer as a case group and 69 samples from apparently healthy females as a control group. Blood samples were collected and sent to Ethiopian Public Health Institute (EPHI) for Serum 25 hydroxyl vitamin D (25(HO) D) Concentration and Thyroid Function Tests , by using a COBAS 6000 analyzer. The data was analyzed using SPSS version 20.0 software. Independent T-tests, chi-square test, One-way ANOVA tests, Kruskal Wallis test, and multiple linear regression tests were used to analyze the data. Results: Breast cancer patients had significantly lower Total Triiodothyronine (TT3) levels(1.2±0.28 ng/mL) than healthy controls (1.4±0.19 ng/mL, p<0.001). Free Triiodothyronine (FT3) was also significantly reduced in BC patients (p< 0.001). 25(HO) D levels showed a significant lower median value in BC patients compared to healthy control groups (p=0.043). Breast cancer stage and subtype significantly influence thyroid function and vitamin D levels, with advanced stages associated with altered thyroid hormones and reduced 25(OH) D levels. Conclusion: Breast Cancer patients exhibited significantly lower TT3 and FT3 levels compared to controls. Although vitamin D deficiency was prevalent in both groups, severe deficiency (<10 ng/mL) was significantly higher in the BC patients. Therefore, monitoring and managing vitamin D and thyroid hormone levels could be important components of breast cancer risk assessment and prevention strategies. However, larger-scale studies are needed to further validate and strengthen these findings.en-USBreast CancerThyroid HormonesTSH25(OH) DVitamin DeficiencyThesis