Canine Thyroid Gland Expresses Luteinizing Hormone Receptors

Hypothyroidism is a complex disease with a net effect of inadequate thyroid hormone receptor activation.1 The incidence of hypothyroidism is 10-15% in postmenopausal women2 and 30% in gonadectomized dogs.3 Circulating luteinizing hormone (LH) concentrations are significantly and persistently elevated in both of these populations. Luteinizing hormone receptors are expressed in normal human thyroid glands.4 We hypothesized that LH receptors were also present in normal canine thyroid glands. The aim of this study was to determine if LH receptors were expressed and to quantify the level of cellular expression. Thyroid and bladder tissue were removed from two dogs (two month old Labrador Retriever female and six month old Labrador Retriever mix spayed female) postmortem, formalin-fixed, paraffin-embedded, and sectioned (6 μm) onto charged slides. Testicular tissue from a separate dog obtained following castration was treated in the same manner. All slides were deparaffinized, rehydrated, subjected to heat-induced epitope retrieval (#S1700, Dako, Carpinteria, CA). Endogenous peroxidase activity was inactivated with 3% H2O2 and nonspecific binding was blocked with 1% horse serum. Goat polyclonal anti-human LHR antibody (SC-26341, Santa Cruz Biotechnology, Dallas, TX,) was applied at a 1:50 dilution. N ...