Luteinizing hormone receptor is immunoexpressed within the canine thyroid

Abstract

Gonadectomy has been implicated as a risk factor for development of canine hypothyroidism, due
to loss of negative feedback to the anterior pituitary, resulting in persistently elevated luteinizing hormone
concentrations. Receptors for luteinizing hormone have been identified in various canine gonadal and
extragonadal tissues, including bladder and skin. The aim was to investigate if luteinizing hormone
receptors were also expressed in the canine thyroid. Formalin-fixed, paraffin-embedded thyroid tissues
from eight dogs of various sexes and breeds were subjected to routine immunohistochemical methods.
Expression of luteinizing hormone receptors was evident in thyrocytes from all thyroid tissue sections
examined; the percentage of positive luteinizing hormone receptors cellular expression was 46.5 ± 23.8%
(mean ± standard deviation). Immunoexpression of luteinizing hormone receptors was localized to
thyroid follicular epithelial cells, with no immunoreactivity in other thyroid constitutive structures or in
any negative control tissue sections. This is apparently the first report to demonstrate luteinizing hormone
receptors expression in the canine thyroid gland. Functional studies are needed to determine whether
unregulated hypersecretion of luteinizing hormone after gonadectomy affects thyroid function.