Common causes

Primary (e.g, Hashimoto disease)

Secondary (e.g., disorders of pituitary or hypothalamus)

Iatrogenic (e.g., thyroidectomy, radioactive iodine therapy)

Inflammation—thyroiditis (e.g., postpartum)

Drug-induced Lithium Glucocorticoids

Graves disease

Inflammation—thyroiditis

Toxic multinodular goiter

Neoplastic—adenomas

Factitious hyperthyroidism

Clinical features

Depression

Weakness

Fatigue

Cold intolerance

Somnolence

Impaired memory

Headache

Constipation

Menorrhagia

Myalgia

Hoarseness

Paresthesias

Anxiety

Heat intolerance

Weight loss

Weakness

Palpitations

Oligomenorrhea

Diarrhea

Exam findings

Hair thinning

Facial and periorbital edema

Presence or absence of goiter

Dry skin

Thin, brittle nails

Delayed deep tendon reflexes

Bradycardia

Non-pitting edema (myxedema)

Mild weight gain

Rare hypoventilation, pericardial or pleural effusions, deafness, carpal tunnel syndrome

Eyelid lag

Stare

Goiter/nodules

Proximal weakness

Brisk deep tendon reflexes

Fine tremor

Tachycardia/atrial fibrillation

Exacerbation of coronary artery disease

Warm, moist skin

Diagnostic findings

Primary hypothyroidism Elevated TSH Decreased free T4

Decreased TSH Elevated free T4 and/or T3

Secondary hypothyroidism Plasma TSH may be within reference levels Other potential findings may include hyponatremia, anemia, elevated lipids, elevated liver enzymes, elevated creatine kinase Of note, many illnesses (e.g., acute psychiatric illness, starvation, autoimmune disease, trauma, surgery, severe illness) can alter thyroid tests without causing thyroid dysfunction

Management

Consult and coordinate care with endocrinology.

Treatment may entail the following:

T4 (levothyroxine) replacement at doses 50-150 mcg daily taken before a meal (lower in elderly and in patients with cardiac disease).

Rule out adrenal insufficiency before starting thyroid hormone replacement therapy.

Consult and coordinate care with endocrinology.

Treatment may entail symptomatic therapy (e.g., beta-adrenergic antagonist), propylthiouracil/methimazole, radioactive iodine, subtotal thyroidectomy.

Urgent intervention is especially required in the setting of exacerbation of heart disease, associated fever, delirium, comorbid medical illness, pregnancy.