Disease of the Thyroid Gland

Where is the thyroid gland located?

Ventral cervical region, lateral edges of the trachea.

Is the normal thyroid gland palpable?

No, normal thyroid is non‑palpable.

What glands are housed within the thyroid?

Parathyroid glands.

What is the function of the parathyroid glands?

Calcium maintenance.

What hormones does the thyroid secrete?

Thyroxine (T4) and calcitonin.

What is the function of thyroxine?

Regulates metabolic activities.

What is the function of calcitonin?

Helps maintain calcium balance.

What hormones increase metabolic activity of cells?

T3 and T4.

Hypothyroidism is most common in which species?

Dogs.

What is the most common form of hypothyroidism?

Primary acquired hypothyroidism.

Causes of primary acquired hypothyroidism?

Thyroid atrophy and lymphocytic thyroiditis.

What is central acquired hypothyroidism?

Rare dysfunction of the hypothalamus-pituitary axis.

What does "poor converters" mean?

Poor conversion of T4 to T3.

What causes clinical signs of hypothyroidism?

Decreased cellular metabolic rate from low thyroid hormone.

Breeds predisposed to hypothyroidism?

Goldens, Dobermans, Setters, Schnauzers, Cockers, Dachshunds.

Clinical signs of hypothyroidism?

Weight gain, PU/PD, bilateral symmetrical alopecia, rat tail, poor coat, heat seeking.

Additional clinical signs of hypothyroidism?

Decreased activity, infertility/anestrus, hyperpigmentation, secondary pyoderma.

What type of anemia occurs with hypothyroidism?

Mild non‑regenerative, normocytic, normochromic anemia.

What metabolic abnormality is common in hypothyroidism?

Hypercholesterolemia.

What is myxedema?

Facial swelling due to glycosaminoglycan accumulation ("tragic face").

Lab findings supporting hypothyroidism?

Elevated cholesterol, mild non‑regenerative anemia.

Diagnostic tests for hypothyroidism?

T3, free T4 (dialysis), TSH levels, TSH stimulation test.

Is T3 reliable for diagnosing hypothyroidism?

No, T3 is less significant.

What is Euthyroid Sick Syndrome?

Non‑thyroid illness lowers T4 but thyroid function is normal.

Drugs that may lower thyroid hormone?

Anticonvulsants and NSAIDs.

Treatment for hypothyroidism?

Thyroid supplementation (Soloxine, Thyro‑tabs, Thyro‑form).

When should hypothyroid patients be rechecked after starting therapy?

4-8 weeks.

What should clients monitor for during thyroid supplementation?

PU/PD, restlessness, panting.

How long do hypothyroid dogs need supplementation?

For life.

Hyperthyroidism is most common in which species?

Cats.

Hyperthyroidism affects what system?

Multisystemic metabolic system.

What causes clinical signs of hyperthyroidism?

Increased basal metabolic rate.

Hyperthyroidism is most common in what age group?

Middle‑aged and older cats.

Most common cause of feline hyperthyroidism?

Functional adenomatous hyperplasia.

Less common cause of feline hyperthyroidism?

Thyroid carcinoma.

What metabolic processes increase in hyperthyroidism?

Heat production, protein metabolism, carbohydrate metabolism, lipid metabolism.

Clinical signs of hyperthyroidism?

Weight loss, restlessness, hyperexcitability, palpable thyroid mass, unkempt coat, excessive shedding.

Additional clinical signs of hyperthyroidism?

Increased appetite, vomiting, PU/PD, dyspnea.

Cardiac signs of hyperthyroidism?

Tachycardia, CHF, gallop murmur, arrhythmia, hypertrophic cardiomyopathy.

Diagnosis of hyperthyroidism?

Palpable thyroid mass, high serum T4.

Differential diagnoses for hyperthyroidism?

Diabetes mellitus, renal disease, IBD, cardiomyopathy.

What imaging confirms hyperthyroidism?

Thyroid radionucleotide uptake scan.

Common antithyroid drug used?

Methimazole.

How does methimazole work?

Inhibits synthesis of thyroid hormones.

Why is PTU not recommended in cats?

Too many side effects.

Surgical treatment for hyperthyroidism?

Thyroidectomy.

What complication may occur after thyroidectomy?

Laryngeal paralysis; must monitor calcium.

Most effective treatment with lowest side effects?

Radioactive iodine therapy.

Dietary treatment option for hyperthyroidism?

Hills y/d.

How is methimazole therapy initiated?

Divided daily doses; some cats managed SID.

When should cats be rechecked after starting methimazole?

2-3 weeks.

What should be monitored during methimazole rechecks?

CBC, platelets, T4.

How are methimazole doses adjusted?

Titrated to effect until T4 reaches normal range.

What two hormones does the thyroid gland secrete?

calcitonin and thyroxine

Most dogs develop acquired _____________________ hypothyroidism?

Primary

Explain what bilateral symmetrical alopecia means.

Hair loss equally on both sides of the body

What type of anemia is commonly associated with hypothyroidism?

Non‑regenerative anemia

normocytic, normochromic

A dog with primary hypothyroidism will typically have a _________________ TSH level.

Elevated

fT4 by ______________________ dialysis is a common test included in a thyroid profile.

Equilibrium

_______________________ cardiomyopathy is commonly associated with feline hyperthyroidism.

Hypertrophic

_________________________ is the most common cause of feline hyperthyroidism.

Functional adenomatous hyperplasia

In feline hyperthyroidism the animal will have a _________________ TSH level.

Decreased

What type of heart murmur is commonly associated with feline hyperthyroidism?

gallop murmur

What is a thyroid slip?

A palpable thyroid nodule that slips under your fingers when you palpate the neck

List at least three clinical signs of canine hypothyroidism.

Weight gain, lethargy, bilateral alopecia

List at least three clinical signs of feline hyperthyroidism.

Weight loss, tachycardia, vomiting

__________________ is the most common drug used to treat feline hyperthyroidism.

Methimazole

What diet can be used to help treat/manage feline hyperthyroidism?

Hill's y/d

Radioactive __________ can be used to treat feline hyperthyroidism.

Iodine