Hyperthyroidism Disease

BASICS

DESCRIPTION

The reaction to excess production of thyroid hormone. Types of hyperthyroidism include:

Graves' disease (GD) - the most common form - an autoimmune disease. Thyroid stimulating immunoglobulins (TSI's) of the IgG class are produced and bind to thyrotropin (TSH) receptors on the thyroid gland. The TSI's mimic the action of TSH and cause excess secretion of thyroxine (T4) and triiodothyronine (T3). Goiter and ophthalmopathy are common characteristics.
Toxic multinodular goiter - occurs late in life. Nodules are insidious and almost never malignant. No ophthalmopathy or localized myxedema present.
Toxic uninodular goiter - solitary nodule with autonomous function. Almost always benign.
Other causes are rare and include TSH-secreting pituitary tumors, surreptitious ingestion of T4 or T3, functioning trophoblastic tumors, and iodine-induced hyperthyroidism, especially from the cardiac drug amiodarone.
System(s) affected: Endocrine/Metabolic
Genetics: Unknown
Incidence/Prevalence in USA: 1:1000 in women, 1:3000 in men
Predominant age: Any age, peaks in 3rd and 4th decades
Predominant sex: Female > Male

SIGNS AND SYMPTOMS

In adults
- Nervousness (85%)
- Increased sweating (70%)
- Heat intolerance (70%)
- Palpitations and tachycardia (75%)
- Dyspnea (75%)
- Fatigue and weakness (60%)
- Weight loss (52%)
- Increased appetite (40%)
- Exophthalmos (34%)
- Goiter (87%)
- Tremor (65%)
- Warm and moist skin (72%)
- Emotional lability
In children
- Linear growth acceleration
- Ophthalmic abnormalities more common

CAUSES

Graves' disease - autoimmune disease
Toxic multinodular goiter - iodine deprivation followed by iodine repletion
Toxic uninodular goiter - unknown

RISK FACTORS

Positive family history
Female sex
Other autoimmune disorders
Iodide repletion after iodide deprivation

DIAGNOSIS

LABORATORY

T3 - Total T3 by immunometric assay > 200 ng/mL
T4 - by immunometric assay > 12.5 µg/dL (161 nmol/L)
Free thyroxine index (FTI) > 12
Free thyroxine > 1.5 ng/dL
TSH - below normal
Radioiodine uptake (RIU) - high in Graves' disease, high or normal in toxic nodules

Drugs that may alter lab results:

Anabolic steroids
Androgens
Estrogens
Heparin
Iodine containing compounds
Phenytoin
Rifampin
Salicylates
Thyroxine
Triiodothyronine

Disorders that may alter lab results:

A variety of non-thyroidal illnesses can alter T4 and T3 with little effect on TSH
FTI permits correction of misleading results caused by pregnancy and estrogens

PATHOLOGICAL FINDINGS

Graves' disease - hyperplasia
Toxic nodules - nodule formation

SPECIAL TESTS

N/A

IMAGING

Thyroid scans using radioiodine: diffuse in GD, focal in toxic nodule

DIAGNOSTIC PROCEDURES

N/A

TREATMENT

APPROPRIATE HEALTH CARE

Outpatient except for treatment of thyroid storm, a life-threatening condition, which may cause heart failure, fever, and mania

GENERAL MEASURES

Antithyroid drugs, therapeutic radioiodine, beta blockers for tachycardia and tremor

SURGICAL MEASURES

Rarely, subtotal thyroidectomy

ACTIVITY

Modify activity according to disease severity

DIET

Sufficient calories to prevent weight loss

PATIENT EDUCATION

Importance of compliance with drug therapy

FOLLOW UP

PREVENTION/AVOIDANCE

N/A

POSSIBLE COMPLICATIONS

Hypoparathyroidism, recurrent laryngeal nerve damage, and hypothyroidism with subtotal thyroidectomy
Development of hypothyroidism after radioiodine treatment
Visual loss or diplopia due to severe ophthalmopathy
Localized pretibial myxedema at any time
Cardiac failure in the elderly with underlying heart disease
Muscle wasting; proximal muscle weakness

EXPECTED COURSE AND PROGNOSIS

With precise diagnosis and adequate treatment, prognosis is good

MISCELLANEOUS

ASSOCIATED CONDITIONS

Other autoimmune diseases and Down syndrome

AGE-RELATED FACTORS

Pediatric: Neonates treated with antithyroids 2-3 months. Most children treated with antithyroids.
Geriatric:

Characteristic symptoms and signs may be absent in elderly
Harder to diagnose
Cardiac failure more likely

Others: N/A

PREGNANCY

Treat with small doses of PTU due to increased risk of spontaneous abortion and premature delivery in hyperthyroid pregnant women
Avoid treatment induced hypothyroidism
Symptoms may be confusing
Thyrotoxicosis often improves during pregnancy and relapses postpartum
Radioiodine therapy absolutely contraindicated

OTHER NOTES

N/A

ABBREVIATIONS

TSI = thyroid stimulating immunoglobulins
TSH = thyroid stimulating hormone
T4 = thyroxine
T3 = triiodothyronine
RIA = radioimmunoassay
FTI = free thyroxine index
RIU = radioiodine uptake
PTU = propylthiouracil
MMI = methimazole

Clinical Investigations

ROLE OF HOMOEOPATHY

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