Dry Eye Dx and Tx
The Hormone-Dry Eye Connection, Part 1
BY WILLIAM TOWNSEND, OD, FAAO
Sex hormones have a long-recognized impact on tear production and ocular surface health (Rocha et al, 2013). More recently, research has also exposed the influence of non-sex hormones on the ocular surface, particularly in regard to tear production (Gadaria-Rathod et al, 2013).
Sex Hormones and Dry Eye
Researchers have conducted numerous studies exploring the influence of sex hormones on tear function and the ocular surface (Sullivan D, Yamagami et al, 2002; Sullivan B et al, 2002; Sullivan D, Schaumberg et al, 2002; Suzuki et al, 2002). Some of the issues addressed by this research include:
- Androgens receptors are found on both lacrimal and meibomian glands and influence their function. Androgens appear to regulate meibomian glands, and androgen deficiency may result in meibomian gland dysfunction (MGD) (Rocha et al, 2013; Sullivan D, Yamagami et al, 2002; Sullivan D, Sullivan B et al, 2002).
- Androgen levels in males and females decline precipitously between ages 30 to 60, but females experience the greatest decrease (Pluchino, 2013; Urbanski, 2013).
- Women who have primary and secondary Sjögren’s syndrome are androgen-deficient, and evidence suggests that androgen deficiency contributes to the overall severe dry eye present in this autoimmune disease (Sullivan D, Sullivan B et al, 2002).
- Animal studies demonstrate that exogenous androgen therapy restored lacrimal gland and meibomian gland anatomy and function (Mostafa et al, 2012; Khandelwal et al, 2012).
- A recent study reported that androgens regulated the expression of more than 3,000 genes in human meibomian gland and conjunctival epithelial cells (Khandelwal et al, 2012).
- In a study comparing males and females who had non-autoimmune MGD to normal controls, individuals who had MGD showed significantly reduced levels of three androgens: bioactive testosterone, dehydroepiandrosterone (DHEA), and DHEA sulphate, suggesting that androgen deficiency in both males and females contributes to MGD (Tamer et al, 2006).
- Sex hormones are emerging as potentially valuable therapeutic agents in managing both aqueous deficient and evaporative dry eye (Worda, 2001).
Thyroid Hormones and Dry Eye
Thyroid disease has long been identified as a potential risk factor for dry eye (Karsh et al, 1980):
- Ismailov et al (2013) investigated the relationship between thyroid eye disease and dry eye.They found structural changes including epithelial dystrophy, cell polymorphism, reduced goblet cell density, desquamation and epithelial keratinization, and localized infiltration. The authors attributed some ocular surface changes to thyroid disease-associated physical changes.
- There is ample evidence that thyroid-associated ocular surface changes also involve pathological thyroid hormone (TH) levels. In an animal model, Dias et al (2007) evaluated the location and comparative expression of thyroid hormone receptor-1 (Thrb) in the lacrimal glands (LG) of rats with hypothyroidism (HT) and in controls. They found that lacrimal gland weight and T4 (free and bound) was reduced, and noted up-regulation of Thrb, attributed by the authors to chronic TH deprivation. Schirmer test results showed a greater than two-fold reduction in tear production in hypothyroid versus controls. CLS
For references, please visit www.clspectrum.com/references.asp and click on document #218.
Dr. Townsend practices in Canyon, Texas, and is an adjunct professor at the University of Houston College of Optometry. He is president of the Ocular Surface Society of Optometry and conducts research in ocular surface disease, lens care solutions, and medications. He is also an advisor to Alcon, B+L, CooperVision, Tearlab Corporation, and Vistakon. Contact him at firstname.lastname@example.org.