Carotid integrated backscatter analysis in patients with subclinical hypothyroidism

Thyroid Dysfunction and Atherosclerosis: A Systematic Review

BACKGROUND/AIM

Thyroid dysfunction, both hypo- and hyperthyroidism, has been associated with cardiovascular disease. The aim of this study was to evaluate the association between thyroid dysfunction and atherosclerosis measured mostly by carotid intima-media thickness, as well as discuss whether L-T4 replacement is able to reverse or slow down the progression of atherosclerosis.

MATERIALS AND METHODS

The review was conducted according the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. We performed on PubMed a literature search from May 2004 to January 2020, using the search terms 'subclinical hypothyroidism' or 'thyroid disorders' and 'carotid artery', 'carotid intima-media thickness (IMT)', 'levothyroxine', and 'atherosclerosis'.

RESULTS

Twenty-six studies were eligible and included in the analysis. Overall, the studies encompassed a total of 36.434 patients included in this review. Most studies indicated a proportional correlation between IMT and thyroid dysfunction. Levothyroxine (L-T4) replacement led to significant decrease of IMT after 1 year in most studies.

CONCLUSION

Most studies have concluded that thyroid dysfunction is associated with arterial wall remodeling and, thus, with increased cardiovascular risk. However, the exact mechanistic background of pathological structural changes in the arterial wall is still unsettled. Large randomized controlled studies are required to definitively address the extent to which T4 replacement therapy might benefit patients with subclinical thyroid disorders.

Metabolic and cardiovascular risk in patients with a history of differentiated thyroid carcinoma: A case-controlled cohort study

Hyperthyroidism seems to increase metabolic and cardiovascular risk, while the effects of sub-clinical hyperthyroidism are controversial. We evaluated metabolic and cardiovascular parameters in differentiated thyroid carcinoma (DTC) patients with suppressed thyrotropin (TSH) due to levo-thyroxine (L-T4) therapy. We studied DTC patients and, as a control group, patients with a history of surgery for non-malignant thyroid pathology. Significantly higher insulin and lower HDL-cholesterol levels were recorded in DTC subjects. In both groups, insulin levels were significantly related with body mass index (BMI) but not with age or L-T4 dosage. In DTC patients, a significant negative correlation was seen between HDL-cholesterol and BMI or L-T4 dosage. In both groups, intima-media thickness (IMT) correlated positively with age, BMI, glucose levels and systolic blood pressure. In DTC patients, increased IMT was significantly correlated with glycated hemoglobin (HbA1c), cholesterol and triglycerides. In DTC patients, C-reactive protein correlated positively with insulin, insulin resistance, triglycerides and systolic blood pressure, and negatively with HDL-cholesterol. In both DTC and control subjects, fibrinogen correlated positively with age, BMI, increased IMT, HbA1c and systolic blood pressure. In DTC subjects, plasma fibrinogen concentrations correlated positively with insulin resistance, cholesterol and LDL-cholesterol, and negatively with TSH levels. Our data confirm that the favorable evolution of DTC can be impaired by a high incidence of abnormal metabolic and cardiovascular data that are, at least in part, related to L-T4 therapy. These findings underline the need for adequate L-T4 titration.