Hypothyroidism is a frequent cause of alopecia in various species, including humans and dogs. Surgical thyroidectomy is often performed on laboratory animals to study thyroid function. While there have been studies into its effects on the function of various internal organs, there are no reports of resulting changes in skin and hair follicle morphology. In a study on rats, the authors showed that decreased expression of thyroid receptors and reduced cell proliferation in hair follicles resulted from a lack of thyroid hormone.
Veterinary Pathology 45 (4): 505-511.