Author:
Todd A.Taylor
Bradley A.Wallace
Description
- Hyperthyroidism is the result of inappropriate secretion of thyroid hormones by the thyroid gland
- Occurs in ∼1.2% of the population in the U.S.
- Excessive thyroid hormone production results in a continuum of disease:
- Subclinical or mild hyperthyroidism
- Thyrotoxicosis
- Thyroid storm or thyrotoxic crisis with life-threatening manifestations:
- 1-2% of patients with hyperthyroidism
- Regulation of thyroid hormone:
- Thyrotropin-releasing hormone (TRH) from hypothalamus acts on the anterior pituitary
- Thyroid-stimulating hormone (TSH) released by anterior pituitary gland and results in increased T3 and T4 from the thyroid gland :
- Most of circulating hormone is T4, which is peripherally converted to T3
- T3 is much more biologically active than T4 although it has a shorter half-life
- The causes of hyperthyroidism can be broken down into 4 categories:
- Excessive thyroid stimulation
- Inappropriate thyroid hormone synthesis
- Stores of hormones are released
- Excessive sources of hormone (endogenous or exogenous)
Etiology
- Primary hyperthyroidism (resulting in inappropriate hormone synthesis):
- Toxic diffuse goiter (Graves' disease)
- Toxic multinodular (Plummer disease) or uninodular goiter
- Excessive iodine intake
- Thyroiditis (thyroid inflammation):
- Postpartum thyroiditis
- Radiation-induced thyroiditis
- Subacute thyroiditis (de Quervain)
- Amiodarone-associated thyroiditis
- Chronic thyroiditis (Hashimoto/lymphocytic)
- Metastatic thyroid cancer
- Ectopic thyroid tissue (struma ovarii)
- Pituitary adenoma
- Drug induced:
- Amiodarone
- Lithium
- α-interferon
- Interleukin-2
- Iodine (radiographic contrast agents)
- Excessive thyroid hormone (factitious thyrotoxicosis)
- Aspirin overdose
ALERT |
Thyroid storm is a life-threatening condition, which may be precipitated by:- Infection
- Trauma
- Diabetic ketoacidosis
- Organophosphate intoxication
- Cytotoxic chemotherapy
- Myocardial infarction
- Cerebrovascular accident
- Surgery
- Abrupt withdrawal of antithyroid medication or acute ingestion of thyroid medication
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Signs and Symptoms
- Signs and symptoms reflect end-organ responsiveness to thyroid hormone:
- Signs:
- Fever
- Tachycardia, wide pulse pressure
- Diaphoresis/sweating
- Congestive heart failure (CHF)
- Shock
- Tremor
- Disorientation/psychosis
- Goiter/thyromegaly
- Thyrotoxic stare/exophthalmos/lid lag
- Hyperreflexia
- Pretibial myxedema
- Symptoms:
- Weight loss
- Dysphagia or dyspnea secondary to obstruction by a goiter
- Rash/pruritus/hyperhidrosis
- Palpitations/chest pain
- Diarrhea and vomiting
- Myalgias and weakness
- Nervousness/anxiety
- Menstrual irregularities
- Heat intolerance
- Insomnia and fatigue
- Thyroid storm involves exaggerated signs and symptoms of thyrotoxicosis:
- Extreme tachycardia and /or atrial fibrillation (AFib)
- Fever
- CHF
- Shock
- Mental status changes
- Thromboembolic events
Geriatric Considerations |
- Apathetic hyperthyroidism:
- Although symptoms are similar to younger population clinical findings are typically more subtle in the geriatric population
- Clinical findings often reflect single-organ system dysfunction:
- CHF
- Refractory AFib
- Weight loss
- Depression, emotional lability, flat affect
- Tremor
- Hyperactivity
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History
Gradual onset of aforementioned signs and symptoms
Physical Exam
- Vital signs:
- Fever
- Tachycardia
- Elevation of systolic blood pressure
- Widened pulse pressure
- Tachypnea/hypoxia
- Alopecia
- Exophthalmos or lid lag
- Thyromegaly or goiter, thyroid bruit
- Fine, thin, diaphoretic skin
- Irregularly irregular heartbeat
- Lung rales (CHF)
- Muscular atrophy/weakness
- Tremor
- Mental status changes/coma
Essential Workup
- Find underlying cause/precipitating factors
- Plasma TSH is the ED test of choice. It is reasonable to initially order TSH, free T4, and free T3:
- A normal TSH level usually rules out hyperthyroidism:
- TSH may be low with normal T4. Get total T3 level to rule out T3 thyrotoxicosis
- If TSH levels unavailable, clinical suspicion should prompt initiation of therapy
Diagnostic Tests & Interpretation
Lab
- Thyroid function tests for:
- Symptoms of hyperthyroidism
- Elderly patient with new-onset CHF
- New AFib/supraventricular tachycardia (SVT)
- Fever of unknown origin
- TSH (usually decreased)
- Free T4 (usually elevated):
- If free T4 is normal send T3 as patients can have T3 thyrotoxicosis
- Lab studies are often not helpful/nonspecific, get as needed to look for underlying causes/precipitants:
- CBC
- Chemistry panel:
- BUN, creatinine may be elevated secondary to dehydration
- Hypokalemia, hyperglycemia
- Liver function tests (increased transaminases)
- ABG for hypoxemia and /or acidosis
- Cardiac markers
- Infectious workup
- There is no universally accepted criteria for the diagnosis of thyroid storm. The Burch-Wartofsky scoring system can be used to predict presence of thyroid storm. Suspect thyroid storm in all sick patients with evidence of hyperthyroidism
Imaging
CXR (in CHF or sepsis)
Diagnostic Procedures/Surgery
ECG:
- Most common: Sinus tachycardia
- Rule out MI as precipitant of thyroid storm
- New-onset AFib
Differential Diagnosis
- Sepsis
- Pheochromocytoma
- Sympathomimetic ingestion
- Psychosis
- Heat stroke
- Delirium tremens
- Malignant hyperthermia
- Neuroleptic malignant syndrome
- Hypothalamic stroke
- Factitious thyrotoxicosis
Prehospital
Stabilization and supportive care
Initial Stabilization/Therapy
- Airway, breathing, and circulation management
- Cardiac monitor
- Supplemental oxygen
- IV fluids
- Initiate cooling measures:
- Acetaminophen for fever:
- Avoid aspirin (displaces thyroid hormone from thyroglobulin, elevates free T4)
- Cooling blanket
ED Treatment/Procedures
- Identify and treat the precipitating event
- For thyroid storm, initiate treatment sequence outlined below based on clinical suspicion
- Inhibit hormone synthesis using thioamides:
- Block hormone release using iodineonly after hormone synthesis is inhibited as above:
- Oral Lugol solution (saturated potassium iodide solution), or
- Iopanoic acid (Telepaque)
- Give iodine at least 1 hr after thioamides to prevent increased hormone production
- Consider lithium in patient allergic to iodine
- Block peripheral effects of thyroid hormone:
- β-blockade:
- Propranolol is first line as it also inhibits T4 conversion to T3
- Esmolol, β-1 selective so may be used in patient with active CHF, asthma, etc.
- Atenolol for outpatient management
- Albumin solution
- Cholestyramine to reduce enteric reabsorption of thyroid hormone
- Dexamethasone/hydrocortisone:
- Prevents peripheral T4-T3 conversion
- Treatment of thyrotoxicosis, secondary thyroiditis:
- β-blockade
- Anti-inflammatory medications
- General thyrotoxicosis support:
- Acetaminophen for hyperpyrexia
- Treat CHF with usual methods
- Manage dehydration with 10% dextrose solution (D 10) to restore depleted hepatic glycogen
- Identify and treat associated and underlying conditions (infection, ketoacidosis, pulmonary thromboembolism, stroke, etc.)
Medication
- Cholestyramine: 4 g PO q.i.d
- Esmolol: 500 mcg/kg IV over 1 min followed by 50 mcg/kg/min IV; titrate to effect
- Hydrocortisone: 300 mg IV initially, followed by 100 mg q8h
- Iopanoic acid: 1 g IV q8h for first 24 hr, then 500 mg IV b.i.d
- Lithium carbonate: 300 mg PO q.i.d (peds: 15-60 mg/kg/d div. t.i.d-q.i.d)
- Lugol solution: 5 drops (250 mg) PO q6h
- MMI: 60-80 mg/d
- Propranolol: 60-80 mg every 4 hr
- PTU: 500-1,000 mg load, then 200-250 mg q4h
First Line
- PTU
- Propranolol
- Iodine therapy (Lugol), 1 hr after PTU
Second Line
Pregnancy Prophylaxis |
- Physiologic changes associated with pregnancy may resemble many symptoms of hyperthyroidism
- Reference ranges for thyroid function tests change during different stages of pregnancy
- Poorly controlled hyperthyroidism during pregnancy may result in:
- Hyperemesis gravidarum
- Premature labor
- Preeclampsia
- Low birth weight
- Spontaneous abortion
- Stillbirth
- Thyroid storm often precipitated by stressors including infection, labor, birth
- Treatment (should be initiated in close conjunction with a specialist):
- Initial stabilization as in the nonpregnant patient (ABCs, supportive measures)
- PTU and MMI both cross the placenta and have been linked to teratogenicity and birth defects
- Propranolol or metoprolol may be safely used
- Radioactive iodine absolutely contraindicated when pregnant or nursing
- Thyroidectomy is the only other option if unable to tolerate PTU while pregnant
- Postpartum thyroiditis:
- 5-10% of patients within 6 mo of delivery
- May require antithyroid medications
- 50% affected become euthyroid within 1 yr
- Transient hypothyroidism may follow
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Disposition
Admission Criteria
- Thyroid storm
- Requiring IV medications to control heart rate
- Significantly symptomatic or unstable patients
Discharge Criteria
Minimal symptoms that respond well to PO therapy
Follow-up Recommendations
- Should have PCP follow-up within a few weeks depending on symptoms
- May benefit from endocrinology referral
- BahnRS, BurchHB, CooperDS, et al. Hyperthyroidism and other causes of thyrotoxicosis: Management guidelines of the American Thyroid Association and American Association of Clinical Endocrinologists . Endocr Pract. 2011;17(3):456-520.
- Klubo-GwiezdzinskaJ, WartofskyL. Thyroid emergencies . Med Clin North Am. 2012;96(2):385-403.
- RossDS, BurchHB. 2016 American Thyroid Association Guidelines for diagnosis and management of hyperthyroidism and other causes of thyrotoxicosis . Thyroid. 2016;26(10):1343-1421.
See Also (Topic, Algorithm, Electronic Media Element)
Hypothyroidism
The authors gratefully acknowledge Rita K Cylulka and Christopher S. Cambell for their contribution to the previous edition of this chapter.