Hyperthyroidism

Published on 10/03/2015 by admin

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Chapter 20 HYPERTHYROIDISM

Theodore O’Connell

Hyperthyroidism is a hypermetabolic state that results from excess synthesis and release of thyroid hormone, usually from the thyroid gland. The overall incidence of subclinical and overt hyperthyroidism is estimated to be 0.05% to 0.1% in the general population. Hyperthyroidism occurs in all age groups and is more common in women than in men. Graves’ disease is the most common cause of hyperthyroidism, causing 60% to 80% of cases. However, toxic nodular goiter is the most common cause of hyperthyroidism in the elderly.

Hyperthyroidism may manifest as a condition in a spectrum ranging from asymptomatic, subclinical hyperthyroidism to life-threatening thyroid storm. Subclinical hyperthyroidism is diagnosed in asymptomatic patients with low levels of thyroid-stimulating hormone (TSH) but normal free thyroxine (T4) and free triiodothyronine (T3). Clinical hyperthyroidism manifests with the typical signs and symptoms outlined later in this chapter.

In elderly patients, the condition often represents a diagnostic challenge because they may have lone symptoms or atypical manifestations. They may have negative symptoms such as depression, lethargy, or apathetic facies. Elderly patients also may have only a small goiter, weight loss, worsening of underlying cardiovascular disease, or new-onset atrial fibrillation.

Medications Linked to Hyperthyroidism

Alemtuzumab (Campath 1-H) (a monoclonal antibody)

Highly active antiretroviral therapy (HAART)

Key Historical Features

✓ Constitutional symptoms

• Excessive perspiration

• Heat intolerance

• Nervousness

• Weight loss

✓ Cardiac symptoms

• Anginal symptoms

• Exertional dyspnea

• Palpitations

• Reduced exercise tolerance

✓ Pulmonary symptoms

✓ Gastrointestinal symptoms

• Difficulty swallowing

• Frequent bowel movements

• Nausea and vomiting

• Rapid intestinal transit time

✓ Genitourinary symptoms

• Urinary frequency

✓ Ophthalmologic symptoms

• Eye irritation or dryness

• Excessive tearing

• Pain with eye movements

• Visual blurring

✓ Reproductive symptoms

• Decreased libido

• Gynecomastia

• Infertility

• Menometrorrhagia

• Oligomenorrhea

• Spider angiomas

✓ Neuromuscular symptoms

• Fatigability

• Generalized weakness

• Proximal muscle weakness

✓ Psychiatric symptoms

• Altered mental status

• Emotional lability

• Memory loss

• Nightmares and vivid dreams

• Poor attention span

• Restlessness

✓ Medical history

✓ Recent pregnancy

✓ Family history

Key Physical Findings

✓ Vital signs, especially signs of tachycardia or hypertension

✓ Skin and hair

• Warm, smooth, velvety skin

• Skin hyperpigmentation

• Palmar erythema

• Pretibial myxedema

• Fine, brittle scalp hair

• Diffuse alopecia

• Nail changes (onycholysis)

✓ Ocular signs

• Exophthalmos

• Infrequent blinking

• Vasodilation of the conjunctiva

• Eyelid or periorbital edema

• Papilledema

✓ Thyroid signs

• Diffuse enlargement

• Single nodule

• Multinodular goiter

✓ Cardiovascular signs

• Tachycardia

• Bounding pulses

• Rapid and brisk carotid upstroke

• Systolic flow murmurs

• Atrial arrhythmias such as atrial fibrillation or atrial flutter

✓ Pulmonary signs

✓ Musculoskeletal signs

• Decreased muscle strength

• Decreased muscle volume

• Muscle atrophy

• Muscle weakness, especially proximal

✓ Neurologic signs

• Brisk reflexes

• Nervousness

• Hyperactivity and rapid speech

Suggested Work-Up

TSH	To evaluate thyroid function
Radionuclide uptake scan	To distinguish Graves disease from thyroiditis and provide anatomic information

Additional Work-Up

Thyroglobulin level	May help distinguish Graves disease (elevated thyroglobulin level) from factitious thyrotoxicosis (decreased thyroglobulin level)
Measurement of thyroid peroxidase antibodies	Elevated levels in Graves disease and lymphocytic thyroiditis

FURTHER READING

Ginsberg J. Diagnosis and management of Graves’ disease. CMAJ. 2003;168:575-585.

McKeown NJ, Tews MC, Gossain VV, et al. Hyperthyroidism. Emerg Med Clin North Am. 2005;23:669-685.

Reid JR, Wheeler SF. Hyperthyroidism: diagnosis and treatment. Am Fam Physician. 2005;72:623-630.

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