Hyperthyroidism Linked to Increased Risks for Breast, Lung, Prostate Cancers – Renal and Urology News

Hyperthyroidism is associated with an increased risk for lung, prostate, and breast cancers, according to study findings published in the European Thyroid Journal.

Although previous study findings have suggested a link between thyroid hormones and cancer cell growth, evidence regarding hyperthyroidism and cancer remains conflicting.

Researchers conducted a register-based nationwide cohort study using 2 primary Danish registries (Danish Civil Registration System and The Danish National Patient Register). Participants were adults with a diagnosis of hyperthyroidism who were matched with 4 reference individuals on the basis of birth month, birth year, and sex.

Exclusion criteria included a previous diagnosis of cancer. Patients were prospectively followed from the index date until migration, death, a registered cancer diagnosis, or the end of the study period.

The primary outcome was the risk for all-cause cancer (excluding thyroid cancer) subsequent to a diagnosis of hyperthyroidism. Secondary outcomes included individual risk for breast, prostate, lung, and colorectal cancers.

The study included 364,494 reference participants and 95,469 patients with hyperthyroidism, of whom 34,366 had Graves disease, 3343 had Graves disease and thyroid associated orbitopathy, 24,173 had toxic nodular goiter (TNG), and 33,040 had unspecified hyperthyroidism. Both groups were followed for a median time of 10-11 years.

The rates of cancer diagnosis were 18.5% and 16.5% among the hyperthyroidism and references groups, respectively. Compared with the reference participants, patients with hyperthyroidism had an increased overall risk for cancer (adjusted sub-distribution hazard ratio [SHR], 1.12; 95% CI, 1.10-1.14).

After stratifying according to cause of hyperthyroidism, the researchers identified increased risks for cancer among patients with TNG (adjusted SHR, 1.17; 95% CI, 1.14-1.20) and Graves disease (adjusted SHR, 1.08; 95% CI, 1.05-1.11).  

Compared with the reference group, patients with hyperthyroidism had increased risks for:

• Lung cancer (adjusted SHR, 1.20; 95% CI, 1.16-1.26);
• Breast cancer (adjusted SHR, 1.07; 95% CI, 1.02-1.13); and,
• Prostate cancer (adjusted SHR, 1.10; 95% CI, 1.02-1.19). 

After stratifying by the cause of hyperthyroidism the researchers identified no increased risk for prostate cancer among patients with Graves disease, whereas the increased risk remained among patients with TNG.

The researchers also observed a statistically significant increased risk for cancer across all age decades. Compared with women, men had a higher risk for all-cause cancer and colorectal cancer. However, this increased risk for colorectal cancer was absent in the stratified analysis according to the cause of hyperthyroidism.

Study limitations include the absence of risk factors such as smoking status and alcohol intake, potential misclassification due to physician error, and the inaccessibility of data on hyperthyroidism treatments.

“In conclusion, this nationwide register-based data demonstrated a 12% increased risk of cancer in a large cohort of hyperthyroid patients,” the researchers wrote. “The risk depended on the type of cancer, with increased SHRs for prostate, breast, and lung cancer, but not for colorectal cancer.”

This article originally appeared on Endocrinology Advisor