Miriam E. Tucker

May 02, 2013

PHOENIX — Just half of primary-care patients with hypercholesterolemia received recommended thyroid-function screening, a new retrospective study has found.

The findings were presented here at the American Association of Clinical Endocrinologists (AACE) 2013 Scientific & Clinical Congress by Devina Willard, MD, an internal-medicine resident at Boston Medical Center, Massachusetts.

Hypothyroidism is an important secondary cause of elevated total cholesterol and LDL cholesterol. In overt hypothyroidism cases, thyroid hormone replacement treatment often normalizes the cholesterol levels. For that reason, guidelines from the AACE, American Thyroid Association, and National Cholesterol Education Program (NCEP) recommend testing for hypothyroidism.

Dr. Willard's study was designed to determine the rate of adherence to the guidelines by primary-care physicians. "The 50% rate of screening is a bit surprising. Although guidelines from the NCEP and [American College of Physicians] ACP state that thyroid dysfunction is [included in the] differential [diagnosis] for new-onset dyslipidemia, the practice of screening in standard clinical practice seems to often be overlooked," she told Medscape Medical News.

Important to Treat Underlying Cause of Hyperlipidemia

Dr. Willard and colleagues reviewed charts from patients aged 18 years and older with total-cholesterol levels of 200 mg/dL and/or LDL-cholesterol levels of 160 mg/dL or above, who were seen at Boston Medical Center's internal-medicine and family-medicine clinics for routine care during 2003 – 2011. Patients who had previously taken lipid or thyroid medications were excluded.

Of the 8795 patients newly diagnosed with hypercholesterolemia, thyroid-stimulating hormone (TSH) levels had been checked within 6 months of the diagnosis for 49%. Peripheral thyroid-function tests were also done for 18.4% of the patients.

Of the total 4349 patients who had TSH levels screened, 151 had TSH levels greater than 5 mIU/L and 74 had TSH levels over 10 mIU/L. Of these 225 patients (with TSH levels >5), 50.7% received levothyroxine treatment, Dr. Willard reported.

Of those 114 patients treated with levothyroxine, 75.4% did not receive a lipid-lowering agent within 1 year, possibly because correction of their hypothyroidism resulted in improvement of their lipid panel and correction of the dyslipidemia, she said.

The clinical implications of the findings are identifying a treatable cause of dyslipidemia and saving on the potential costs of long-term management of cholesterol-lowering therapy in many individuals, as well as reducing risk for cardiovascular events, Dr. Willard told Medscape Medical News.

She added, "We agree with the guidelines… It is important to treat the underlying and potentially reversible cause of dyslipidemia. However, we would conclude that more research is needed to better assess the cost/benefit effectiveness of having these guidelines be universally adopted."

Dr. Willard has reported no relevant financial relationships.

American Association of Clinical Endocrinologists 2013 Scientific & Clinical Congress. Abstract 1061, presented May 2, 2013.