Primary hypothyroidism associated with leishmaniasis in a dog

A case of primary hypothyroidism associated with leishmaniasis is described in a four-year-old, male Yorkshire terrier. Clinical diagnosis of hypothyr oidism was confirmed by a low baseline serum tetraiodothyronine (T-4), a re duced response to thyroid-stimulating hormone (TSH) stimulation, an increas ed serum TSH concentration, and scintigraphic thyroid gland examination. Ex amination of a thyroid biopsy showed many Leishmania amastigotes, both insi de and outside of macrophages, together with signs of follicular atrophy.