Thyroid Dysfunction and 10-Year Incidence of AMD
Investigative Ophthalmology & Visual Science
Epidemiological evidence on the possible relationship between thyroid dysfunction and age-related macular degeneration (AMD) is unclear. Thus, Gopinath et al. analyzed data from the Blue Mountains Eye Study (BMES) to assess the prospective associations between serum thyroid-stimulating hormone (TSH) and free thyroxine (FT4) measurements, as well as thyroid dysfunction (hyperthyroidism and hypothyroidism) and the incidence of AMD. They found an independent association between overt hyperthyroidism and the incidence of AMD; thyroxine usage was also associated with AMD.
Categories of thyroid dysfunction were defined according to a serum TSH screen followed by serum FT4 assessment, and were available for 906 participants aged 55 years or older (the age group at risk for AMD). These parameters were not recorded at the original BMES baseline. Thus, the time frame for this study spanned BMES-2, 1997-1999, to BMES-3, 2007-2009. AMD was assessed from retinal photographs. The researchers also studied covariates, including history of smoking, frequency of consuming fish, and the presence of an AMD susceptibility gene.
After adjusting for covariates, the researchers found that participants with overt hyperthyroidism (low TSH and high FT4 levels) had a 3-fold increased risk of developing incident AMD compared with participants with normal thyroid function (odds ratio [OR], 3.51). Thyroxine usage was also positively associated with the incidence of AMD; those who reported current use of thyroxine had increased risk of incident AMD compared with nonusers (OR, 1.68). Similarly, participants who had ever taken thyroxine medication had a higher risk of AMD (OR, 1.91) than those who had never taken the drug. However, baseline serum TSH or FT4 levels per se did not show an association with 5- or 10-year incidence of AMD.
The researchers concluded that improved knowledge of risk factors could help to develop comprehensive screening strategies for AMD. They suggested that consideration of thyroid disease might contribute to a better profiling of AMD in clinical practice.
The original article can be found here.