Table 3.

Effects of various drugs in coexistent diabetes and thyroid disorders

Drugs	Effects of anti-diabetic drugs on thyroid function in patients with T2DM
Biguanides (metformin) [53, 54]	Reduces TSH level Reduces risk of thyroid cancer Reduces thyroid volume and nodule size May be a promising therapy for patients with TD
Sulfonylureas [55]	Increases the risk of thyroid cancer Increases risk of hypothyroidism and goitre
Thiazolidinediones [24, 56]	Inhibits the activity of thyroid hormone receptors Increases TSH Increases IGF-1 Decreases FT4 Aggravates thyroid-associated orbitopathy

Drugs	Effects of anti-thyroid drugs on glycaemic control
Methimazole [24]	Is related to the development of insulin autoimmune syndrome May cause hypoglycaemia in patients with diabetes
Carbimazole [57]	Insulin autoimmune syndrome has been reported
Levothyroxine [58]	Reduces fasting and postprandial glucose levels Reduces the glycosylated haemoglobin level

T2DM type 2 diabetes mellitus, TSH thyroid-stimulating hormone, TD thyroid disorder, IGF1 insulin-like growth factor-1, FT4 free thyroxine