Association Between Keratoconus and Thyroid Gland Dysfunction: A Cross-Sectional Case–Control Study

Abstract

K eratoconus is a corneal ectatic disorder that starts at puberty and decreases the radius of curvature of the central cornea. 1 Kennedy et al. 2 reported that the incidence rate is 1 per 50,000 among the population. Moreover, the pathophysiological processes underlying keratoconus have not been fully explained and proposed mechanisms including oxidative dam-age, proteolytic degradation in the corneal stroma, epithelial mechanical injury, immunological factors, and genetic factors have been suggested. [1][2][3][4] reported an incidence of keratoconus in 3.5% to 8% of patients with Down syndrome. Furthermore, hormonal imbalances affect the corneal metabolism and may be associated with keratoconus. Likewise, thyroid gland ABSTRACT PURPOSE: To examine the clinical association between thyroid gland dysfunction and keratoconus. METHODS:This was a cross-sectional case-control study conducted between May 2018 and July 2019. After performing Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany) examination, flat, steep, and maximum simulated keratometric readings were recorded for each patient. Serum concentrations of free triiodothyronine, free thyroxine, and thyroidstimulating hormone were measured. Further examinations by an endocrinologist were indicated for patients with positive laboratory results to confirm thyroid gland dysfunction. RESULTS:One hundred eighty-seven patients with bilateral keratoconus and 187 sex-and age-matched healthy controls without keratoconus were analyzed. Mean age was 26.4 ± 8.2 years for the patients with keratoconus and 27.1 ± 9.4 years for the control patients, with no significant difference. The results showed that thyroid gland dysfunction prevalence was 10 of 187 patients with keratoconus (5.3%) and 2 of 187 control patients (1.1%), and the difference was statistically significant (P = .036). For the patients with keratoconus and thyroid gland dysfunction, 8 were women and 2 were men. Additionally, 6 patients (2 men and 4 women) had hyperthyrosis and 4 women had hypothyrosis. For controls, the two patients had hypothyrosis. CONCLUSIONS:This study showed that there is a possible association between keratoconus and thyroid gland dysfunction, but more studies are needed to build upon these results.[J Refract Surg. 2020;36(4):253-257.] (AT). © 2020 El-Massry, Doheim, Iqbal, et al.; licensee SLACK Incorporated. This is an Open Access article distributed under the terms of the Creative Commons . This license allows users to copy and distribute, to remix, transform, and build upon the article non-commercially, provided the author is attributed and the new work is non-commercial.

Impact of Hypothyroidism on Tomography and Biomechanics in Keratoconus – Cross-Sectional and Longitudinal Assessment within the Homburg Keratoconus Center at the Time of Inclusion and after 1 Year

“…However, the higher prevalence was regardless of the type of thyroid dysfunction. Moreover, the prevalence in their control group was lower than the previously reported prevalence of thyroid dysfunction in adults in the general population (3.82%) in Europe 30 , 31 . This can possibly be explained by environmental factors comparing Arab/Middle Eastern countries and Europe.…”

Impact of Hypothyroidism on Tomography and Biomechanics in Keratoconus – Cross-Sectional and Longitudinal Assessment within the Homburg Keratoconus Center at the Time of Inclusion and after 1 Year

“…However, the higher prevalence was regardless of the type of thyroid dysfunction. Moreover, the prevalence in their control group was lower than the previously reported prevalence of thyroid dysfunction in adults in the general population (3.82%) in Europe 30 , 31 . This can possibly be explained by environmental factors comparing Arab/Middle Eastern countries and Europe.…”

Keratoconus: The Local Manifestation of a Systemic Disease?

“…Additionally, such patients showed increased maximum simulated keratometry value and thinner corneas [193]. This association has been confirmed by different authors, who have found a higher incidence of KC in the female sex and in association with hyperthyroidism [192,194]. On the contrary, no association was found between congenital hypothyroidism diagnosed and treated from newborn age and KC [195], and the severity of KC does not seem to change depending on the presence of hypothyroidism [196].…”

Ten-year incidence of keratoconus in relation to sex, age, and thyroid gland dysfunction: a nationwide population-based cohort study (2009–2018)

“…Unlike cohort studies previously published in Korea, we focused on the development of keratoconus in patients with TGD. In the present study, our large sample size of over 4 million people is advantageous, while previous studies on the relationship between thyroid and keratoconus have used small samples ( 8 , 10 , 11 ). Since all citizens in South Korea are obliged to register for health insurance at birth, this data is ideal for epidemiological research ( 13 ).…”

Impact of Hypothyroidism on Tomography and Biomechanics in Keratoconus – Cross-Sectional and Longitudinal Assessment within the Homburg Keratoconus Center at the Time of Inclusion and after 1 Year

“…However, the higher prevalence was regardless of the type of thyroid dysfunction. Moreover, the prevalence in their control group was lower than the previously reported prevalence of thyroid dysfunction in adults in the general population (3.82%) in Europe 30 , 31 . This can possibly be explained by environmental factors comparing Arab/Middle Eastern countries and Europe.…”

Keratoconus: The Local Manifestation of a Systemic Disease?

“…Additionally, such patients showed increased maximum simulated keratometry value and thinner corneas [193]. This association has been confirmed by different authors, who have found a higher incidence of KC in the female sex and in association with hyperthyroidism [192,194]. On the contrary, no association was found between congenital hypothyroidism diagnosed and treated from newborn age and KC [195], and the severity of KC does not seem to change depending on the presence of hypothyroidism [196].…”

Ten-year incidence of keratoconus in relation to sex, age, and thyroid gland dysfunction: a nationwide population-based cohort study (2009–2018)

“…Unlike cohort studies previously published in Korea, we focused on the development of keratoconus in patients with TGD. In the present study, our large sample size of over 4 million people is advantageous, while previous studies on the relationship between thyroid and keratoconus have used small samples ( 8 , 10 , 11 ). Since all citizens in South Korea are obliged to register for health insurance at birth, this data is ideal for epidemiological research ( 13 ).…”

Impact of Hypothyroidism on Tomography and Biomechanics in Keratoconus – Cross-Sectional and Longitudinal Assessment within the Homburg Keratoconus Center at the Time of Inclusion and after 1 Year

“…However, the higher prevalence was regardless of the type of thyroid dysfunction. Moreover, the prevalence in their control group was lower than the previously reported prevalence of thyroid dysfunction in adults in the general population (3.82%) in Europe 30 , 31 . This can possibly be explained by environmental factors comparing Arab/Middle Eastern countries and Europe.…”

Keratoconus: The Local Manifestation of a Systemic Disease?

“…Additionally, such patients showed increased maximum simulated keratometry value and thinner corneas [193]. This association has been confirmed by different authors, who have found a higher incidence of KC in the female sex and in association with hyperthyroidism [192,194]. On the contrary, no association was found between congenital hypothyroidism diagnosed and treated from newborn age and KC [195], and the severity of KC does not seem to change depending on the presence of hypothyroidism [196].…”

Ten-year incidence of keratoconus in relation to sex, age, and thyroid gland dysfunction: a nationwide population-based cohort study (2009–2018)

“…Unlike cohort studies previously published in Korea, we focused on the development of keratoconus in patients with TGD. In the present study, our large sample size of over 4 million people is advantageous, while previous studies on the relationship between thyroid and keratoconus have used small samples ( 8 , 10 , 11 ). Since all citizens in South Korea are obliged to register for health insurance at birth, this data is ideal for epidemiological research ( 13 ).…”