General Information

Hypothyroidism is a condition resulting from a deficiency of thyroid hormone which is produced in the thyroid gland. The thyroid is located in the neck near the larynx (voice box).

Thyroid hormone is involved with cellular metabolism. Its deficiency may result in hair loss especially on the trunk except in large breeds where it may begin on the legs. This is due to atrophy of the hair follicle and cessation of hair production. The hairs are dry and brittle. Other sign of hypothyroidism may include increased pigmentation and thickness of the skin, mental dullness, intolerance to cold, lethargy, infertility, and weight gain.

A secondary complication of hypothyroidism may be seborrhea which is a dry scaling (dandruff) or greasy crusting skin disorder that may or may not be itchy. Recurrent skin and external ear infections may also occur.

Hypothyroidism occurs most frequently in middle-aged or older dogs although it can appear at a much younger age in larger breeds.


Diagnosis involves obtaining a small blood sample for thyroid hormone level evaluation. When circulating levels of the hormone are low a diagnosis is made.

Equivocal test results sometimes warrants TSH response test. This test evaluates thyroid function by its response to Thyroid Stimulating Hormone.

Response to thyroid hormone supplementation supports the diagnosis.


A thyroid hormone product is used to treat hypothyroidism. Because of the higher metabolic turn-over, dogs often require medication twice daily as compared to the once a day requirement in people. The dosage for dogs is much higher than humans.

Post Pill Test: We would like to see your dog_________weeks after initiation of treatment to assure that he/she is on the proper dosage. On that day your dog should receive his/her morning medication ________ yours prior to your scheduled appointment.

Treatment is lifelong with possible dosage adjustments with increasing age. Therefore, a post-pill test is recommended yearly with the routine annual physical exam. An appointment should be made for __________ hours after the morning medication is given.

Hypothyroidism is very amenable to treatment though a visible response takes time. YOu should expect to see changes in activity within 1-2 weeks. The hair should start to regrow in 4-6 weeks.

Thyroid hormone alone will not completely correct associated skin conditions therefore medicated shampoos and antibiotics are prescribed when indicated.

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