Influence of Thyroid Hormone on Thyroid Hormone Receptor β-1 Expression and Lacrimal Gland and Ocular Surface Morphology

Abstract

Chronically reduced levels of TH lead to biochemical and structural changes and modulate the levels of Thrb in LG. These events confirm that LG is a target organ for TH and may facilitate understanding of the mechanism related to dry eye in hypothyroidism.

Evaluation of the Relationship Between Thyroid Functions and Dry Eye Symptoms in Patients with Hashimoto Thyroiditis

“…This relation may be explained by the fact that most of the effects of thyroid hormones on peripheral receptors are mediated by fT3 levels (16). The etiopathogenesis of dry eye syndrome related with TAO have been investigated in several recent studies (7,(9)(10)(11)(12). One of the main factors is an increase in tear film evaporation due to proptosis which subsequently causes tear hyperosmolarity and a decreased TBUT (17,18).…”

“…The majority of the studies pertaining to dry eye syndrome and TAO have been conducted with Graves patients (7,9,11,12) and it has been seen that the studies on Hashimoto thyroiditis are rather limited (12,15). Previous experiments have shown that chronic deficiency of thyroid hormones causes ocular surface abnormalities and dry eye syndrome (10). In 2007, Dias et al suggested that lacrimal glands express receptors of thyroid hormone β-1 (Thrb), due to which they become a target tissue for thyroid hormones and thereby are susceptible to hypothyroidism.…”

“…In 2007, Dias et al suggested that lacrimal glands express receptors of thyroid hormone β-1 (Thrb), due to which they become a target tissue for thyroid hormones and thereby are susceptible to hypothyroidism. Furthermore, the chronic deficiency of thyroid hormones has been shown to be related to a modification in Thrb receptor expression, leading to diminished tear secretion and dry eye syndrome (10). Thyroid hormone regulates the oxidative metabolism through its nuclear Thrb receptors and therefore chronic hypothyroidism results in increased oxidative stress (22,23).…”

“…Thyroid hormone regulates the oxidative metabolism through its nuclear Thrb receptors and therefore chronic hypothyroidism results in increased oxidative stress (22,23). Immunohistochemical analysis indicates the presence of Thrb receptors in the acinar and ductal cells of lacrimal glands and in the nuclei of epithelial cells that line the corneal and conjunctival surface and it has been seen that these receptors are upregulated during hypothyroidism (10). Hence, the presence of hypothyroidism may have an adverse effect on lacrimal gland as well as corneal and conjunctival epithelial cells which are susceptible to low thyroid hormone levels (via Thrb receptors).…”

“…Additionally, the effect of several inflammatory cytokines such as IL1-α, IL-4, and IGF-1 may play a role in this process (8). Recently, in addition to these factors, thyroid hormone receptors β-1 (Thrb-1), which are located on lacrimal glands, were found to be responsible for the development of dry eye (10). These receptors are known to cause susceptibility toward hypothyroidism, by converting the lacrimal glands as a target tissue for thyroid hormones.…”