An underactive thyroid (also known as hypothyroidism), can have a number of causes: it may be congenital, spontaneous, or an expression of various diseases (such as autoimmune thyroiditis) or can arise as a result of surgery to, or irradiation of, the thyroid gland.
Hypothyroidism has a direct effect on the biomechanics of the cornea. The exact mechanism of action is not yet known. Under certain circumstances, hypothyroidism may affect keratoconus and may be a contra-indication for (reason not perform) perform laser refractive surgery.
In addition, many women have an underactive thyroid during pregnancy.
A connection between hypothyroidism and keratoconus has been suspected for decades:
A scientific article of Prof. Hafezi’s, published in 2014 in the Journal of Refractive Surgery clearly showed the association between hyperthyroidism and changes in corneal topography. Such changes are then accompanied by considerable fluctuations in vision.