Table 4.

Key scientific evidence on the effect of treatments for PCOS on thyroid function and disease according to the Oxford Centre for Evidence-Based Medicine 2011 Levels of Evidence (http://www.cebm.net/index.aspx?o=5653).

PCOS treatment	Thyroid effect	Grade of evidence
Lifestyle modification programs (diet and physical activity)	Controversial data on thyroid hormones levels and development of thyroid cancer	Level 3
Metformin	Controversial data on potential reduction in serum TSH levels and thyroid nodule size	Level 2
Oral contraceptives and anti-androgens	Potential risk of hypothyroidism development Potential increased risk of thyroid cancer	Level 3
Vitamin D	Low vitamin D levels are potentially correlated with PCOS and AIT development	Level 2
Myoinositol	Improvement of SCH and AIT	Level 5

AIT, autoimmune thyroid disease; PCOS, polycystic ovary syndrome; SCH, subclinical hypothyroidism; TSH, thyroid stimulating hormone.