Diabetes Risk Linked With Hypothyroidism

Hypothyroidism increases the risk of diabetes, but in subclinical hypothyroidism the increased risk is prominent only with statin use.

Hypothyroidism is a risk factor for new-onset diabetes mellitus (DM), according to the results of a new study. In subclinical hypothyroidism, however, the risk increases only with statin use.

“Hypothyroidism is a risk factor for DM. Subclinical hypothyroidism-associated risk for DM is prominent only upon statin use,” wrote the researchers, led by Naomi Gronich, MD, from the Israel Institute of Technology in Haifa.

Thyroid dysfunction is common in patients with DM and can produce significant metabolic disturbances. Regular screening for thyroid abnormalities in all of these patients is recommended to allow for early treatment of subclinical thyroid dysfunction.

Insulin resistance plays a pivotal role in the underlining relation between type 2 DM and thyroid dysfunction. Clinical studies show a role of thyroid malfunctioning as a comorbid disorder of type 2 DM.

In a 2-phase study, Gronich and colleagues examined risk factors for the development of statin-associated DM. In phase 1, risk factors were identified in a high-throughput in silico processing phase. In phase 2, the most prominent risk factor identified was confirmed in an observational cohort study at the largest health care organization in Israel.

Nearly 40,000 statin nonusers were propensity score–matched with more than 20,000 highly compliant statin initiators in 2004 to 2005. The researchers monitored the patients through 2010.

A multivariable model found that hypothyroidism (rate ratio, 1.53) and subclinical hypothyroidism (rate ratio, 1.75) correlated with an increased risk of DM among statin users and nonusers. “Hypothyroidism increased DM risk irrespective of statin treatment,” they wrote, with rate ratios of 2.06 in statin users and 1.66 in nonusers.

Subclinical hypothyroidism also correlated with increased DM risk but only for statin users; rate ratios were 1.94 for statin users and 1.2 for nonusers.

Patients treated with thyroid hormone replacement therapy for hypothyroidism were not at increased risk for DM.

The researchers noted that future clinical studies are needed to confirm their findings.

They reported their results online June 12, 2015, in Diabetes Care.