Endocrine Abstracts

The prevalence and possible excess risk of thyroid cancer in T1D compared to individuals without T1D is poorly known. Therefore, the aim of this study was to assess excess risk of thyroid cancer in adults with long-term T1D compared to sex- and age-matched control individuals.

Study included 4758 individuals with T1D from the Finnish Diabetic Nephropathy (FinnDiane) Study. For each individual, three nondiabetic control individuals who were matched for sex, age, and place of residence in the year of diagnosis of diabetes in the FinnDiane patient, were selected from the Finnish Public Registry, altogether 12710. The thyroid cancers were identified by linking the data with the Finnish Care Register for Health Care (data available for the years 1970–2015). The types of cancers as well as the presence of metastaseswere assessed by reviewing the medical records. Cochran–Mantel–Haenszel test was used to compare risks and produce odds ratios (ORs)with 95% confidence intervals (CI) between individuals with T1D and controls.

The median age of the FinnDiane individuals at the end of follow-up in 2015 or death was 51.4 (IQR 42.6–60.1) years. As many as 27 (0.57%) had thyroid cancer, compared to 27 (0.21%) in the control individuals giving rise to an OR of 2.67 (95% CI 1.57–4.56, P = 0.0002). The median age at diagnosis of thyroid cancer was 38.5 years (IQR 33.6–46.6) in T1D and 42.8 years (29.4–49.9) in controls (P = 0.83). Women had higher risk in the controls (OR = 3.07 (1.30–7.26) while the risk in T1D was no different between the sexes, OR = 1.61 (0.74–3.47). Median HbA1c was 8.8% (8.2–9.5) in those with T1D and thyroid cancer while it was 8.3% (7.4–9.2) in the rest of the FinnDiane individuals (P < 0.0001). 16.7% of thyroid cancers were associated with thyroid autoimmunity.

The distribution of different types of thyroid cancers was similar in those with T1D and the controls. Most of the cancers were papillary; 81.5% in T1D and 88.9% in the controls, while 14.8% were follicular in T1D and 11.1% in the controls. There was only one medullary cancer in T1D. Signs of metastases were observed in 2 out of 27 individuals with T1D and in 7 out of 27 in the controls (P = 0.12).

The prevalence of thyroid cancer is 2.7 fold in individuals with T1D and equal between the sexes. The data suggest that poor glycemic control is associated with risk of thyroid cancer in T1D.