Simple goiter
Simple (or nontoxic) goiter is a thyroid gland enlargement that isn’t caused by inflammation or a neoplasm, and is commonly classified as endemic or sporadic. Endemic goiter usually results from inadequate dietary intake of iodine associated with such factors as iodine-depleted soil or malnutrition. Sporadic goiter follows ingestion of certain drugs or foods.
Simple goiter affects more females than males, especially during adolescence, pregnancy, and menopause, when the body’s demand for thyroid hormone increases. Sporadic goiter affects no particular population segment. With appropriate treatment, the prognosis is good for either type of goiter.
Causes and incidence
Simple goiter occurs when the thyroid gland can’t secrete enough thyroid hormone to meet metabolic requirements. As a result, the thyroid gland enlarges to compensate for inadequate hormone synthesis, a compensation that usually overcomes mild to moderate hormonal impairment. Because thyroid-stimulating hormone (TSH) levels are generally within normal limits in patients with simple goiter, goitrogenicity probably results from impaired intrathyroidal hormone synthesis and depletion of glandular iodine, which increases the thyroid gland’s sensitivity to TSH. However, increased levels of TSH may be transient and therefore missed.
Endemic goiter usually results from inadequate dietary intake of iodine, which leads to inadequate secretion of thyroid hormone. Since the introduction of iodized salt in the United States, cases of endemic goiter have virtually disappeared.
Sporadic goiter commonly results from the ingestion of large amounts of goitrogenic foods or the use of goitrogenic drugs. Goitrogenic foods, such as rutabagas, cabbage, soybeans, peanuts, peaches, peas, strawberries, spinach, and radishes, contain agents that decrease thyroxine (T4) production. Goitrogenic drugs include propylthiouracil, iodides, phenylbutazone, para-aminosalicylic acid, cobalt, and lithium. In a pregnant woman, these substances may cross the placenta and affect the fetus.
Inherited defects may be responsible for insufficient T4 synthesis or impaired iodine metabolism. Because families tend to congregate in a single geographic area, this familial factor may contribute to the incidence of both endemic and sporadic goiters.
Females are more commonly affected than males. Incidence increases after age 40.
Signs and symptoms
Thyroid enlargement may range from a mildly enlarged gland to a massive, multinodular goiter. (See Massive goiter, page 840.) Because simple goiter doesn’t alter the patient’s metabolic state, clinical features arise solely from enlargement of the thyroid gland. The patient may complain of respiratory distress and dysphagia from compression of the trachea and esophagus, and swelling and distention of the neck. In addition, large goiters may obstruct venous return, produce venous engorgement and, in rare cases, induce development of collateral venous circulation in the chest. Obstruction may cause dizziness or syncope (Pemberton’s sign) when the patient raises her arms above her head.
Diagnosis
Diagnosis of simple goiter requires a thorough patient history and physical examination to rule out disorders with similar clinical effects, such as Graves’disease, Hashimoto’s thyroiditis, and thyroid carcinoma. A detailed patient history may also reveal goitrogenic medications or foods or endemic influence. The results of diagnostic laboratory tests include the following:
❑ TSH: high or normal levels
❑ Serum T4 concentrations: low normal or normal
❑ Thyroid scan and uptake: normal or increased (50% of the dose at 24 hours)
❑ Ultrasound of thyroid: nodules may be present, necessitating biopsy for further evaluation.
Treatment
The goal of treatment is to reduce thyroid hyperplasia. Exogenous thyroid hormone replacement with levothyroxine is the treatment of choice; it inhibits TSH secretion and allows the gland to rest. Small doses of iodide (Lugol’s or potassium iodide solution) commonly relieve goiter that’s due to iodine deficiency. Sporadic goiter requires avoidance of known goitrogenic drugs and foods. A large goiter that’s unresponsive to treatment may require subtotal thyroidectomy.
Special considerations
Patient care includes measuring the patient’s neck circumference daily to check for progressive thyroid gland enlargement, and checking for the development of hard nodules in the gland, which may indicate carcinoma.
❑ To maintain constant hormone levels, instruct the patient to take the prescribed thyroid hormone preparations at the same time each day. Advise her to avoid taking the medicine at the same time as any calcium or iron-containing supplements (including prenatal vitamins), or with Metamucil, grapefruit, or grapefruit juice. Teach the patient and her family to identify and immediately report signs of thyrotoxicosis, including increased pulse rate, palpitations, diarrhea, sweating, tremors, agitation, and shortness of breath.
❑ Instruct the patient with endemic goiter to use iodized salt to supply the daily 150 to 300 mcg of iodine necessary to prevent goiter.
❑ Monitor the patient taking goitrogenic drugs for signs of sporadic goiter.
Pictures
Book Source Details
- Book Title: Professional Guide to Diseases (Eighth Edition)
- Author(s): Springhouse
- Year of Publication: 2005
- Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.
Other Book Chapters Related to Goiter
Read excerpts from these other book chapters related to Goiter:
Medical Books Excerpts
- Thyroid Nodule
- "The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter" (2000)
- [ read ]
- Goiter
- "The 5-Minute Pediatric Consult" (2008)
- [ read ]
Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2008 Williams & Wilkins.
More About Causes of Goiter
» Next page: Thyroid enlargement (Professional Guide to Signs & Symptoms (Fifth Edition))
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