Diabetes, a group of metabolic disorders manifested as high blood sugar levels over a prolonged period, is the most common chronic endocrine disease. Chronic diabetic hyperglycemia is associated with long-term organ damage, dysfunction, and failure. Complications, such as vision loss, renal failure, and cardiovascular diseases, are often outcomes of diabetes. As the population ages and obesity increases, diabetes will increase as well. Thus, diabetes has reached epidemic proportions worldwide, and this burdens healthcare services and increases healthcare costs.

Numerous epidemiological studies indicate the higher prevalence of overt hypothyroidism in type 2 diabetes mellitus (T2DM) or metabolic syndrome population compared to that in the general population. However, the relationship between subclinical hypothyroidism (SCH) and T2DM is controversial. SCH, the slight hypothyroidism state, is asymptomatic but mild elevations in thyroid-stimulating hormone (TSH) with normal circulating free thyroid hormone concentrations are observed. Currently, controversy persists about indications for treatment of SCH and whether individuals should be routinely screened for this dysfunction.

In order to find out more evidence to reveal the relationship between subclinical hypothyroidism and diabetes or metabolic syndrome, we launched a special issue focused on this area. We hope to attract studies based on either basic research or clinical studies. Review articles focusing on this specific topic are encouraged as well. As for basic research, either in vivo or in vitro studies are welcomed. As for clinical studies, either follow-up studies, cross-sectional studies, community-based studies, or hospital-based studies are encouraged.

Potential topics include but are not limited to the following:

• The prevalence of subclinical hypothyroidism in patients with diabetes or metabolic syndrome
• The prevalence of thyroid autoimmunity in patients with diabetes or metabolic syndrome
• The prevalence of diabetes in patients with subclinical hypothyroidism
• The prevalence of metabolic syndrome or diabetes in patients with subclinical hypothyroidism
• The prevalence of metabolic syndrome or diabetes in patients with thyroid autoimmunity
• The relationship between subclinical hypothyroidism and diabetic nephropathy
• The relationship between subclinical hypothyroidism and diabetic retinopathy
• The relationship between subclinical hypothyroidism and diabetic peripheral neuropathy
• The relationship between subclinical hypothyroidism and diabetic cardiopathy
• The relationship between subclinical hypothyroidism and diabetic peripheral arterial disease