Goiter therapy

The common causes of thyrotoxicosis are shown in Table 41-6.29,30 Thyrotoxicosis can be related to the presence or absence of excess hormone production (hyperthyroidism). Graves disease is the most common cause of hyperthyroidism. Thyrotoxicosis in the elderly is more likely due to toxic thyroid nodules or multinodular goiter than to Graves disease. Excessive intake of thyroid hormone may be due to overtreatment with prescribed therapy. Surreptitious use of thyroid hormones also may occur, especially in health professionals or as a self-remedy for obesity. Thyroid hormones can be obtained easily without a prescription from health food stores or Internet sources. 

Subtotal thyroidectomy is indicated in patients with very large goiters and thyroid malignancies and those who do not respond or cannot tolerate other therapies. Patients must be euthyroid prior to surgery, and patients often are administered iodide preoperatively to reduce gland vascularity. The overall surgical complication rate is 2.7%. Postoperative hypothyroidism occurs in 10% of patients who undergo subtotal thyroidectomy. 

Up to 30% of patients on maintenance lithium therapy develop transiently elevated serum concentrations of thyroid-stimulating hormone, and 5% to 35% of patients develop a goiter and/or hypothyroidism, which is dose-related and more likely to occur in women. This is managed by adding levothyroxine to the regimen. 

Thyroid suppression therapy of euthyroid goiter (B). The cause of goiter (struma) is usually a dietary deficiency of iodine. Due to an increased TSH action, the thyroid is activated to raise utilization of the little iodine avail-Liillmann, Color Atlas of Pharmacology 2000 Thieme All rights reserved. Usage subject to terms and conditions of iicense. 

Autoimmune polyglandular syndrome-Chron c autoimmune thyroiditis may occur in association with other autoimmune disorders. Treat patients with concomitant adrenal insufficiency with replacement glucocorticoids prior to initiation of treatment. Failure to do so may precipitate an acute adrenal crisis when thyroid hormone therapy is initiated. Patients with diabetes mellitus may require upward adjustments of their antidiabetic therapeutic regimens. Nontoxic diffuse goiter or nodular thyroid disease Use caution when administering levothyroxine to patients with nontoxic diffuse goiter or nodular thyroid disease in order to prevent precipitation of thyrotoxicosis. If the serum TSH is already suppressed, do not administer levothyroxine. 

Refetoff S, Ochi Y, Selenkow HA, Rosenfield RL. Neonatal hypothyroidism and goiter in one infant of each of two sets of twins due to maternal therapy with antithyroid drugs. J Pediatr 1974 85(2) 240-4. 

Hershey CO, McVeigh RC, Miller RP. Transient superior vena cava syndrome due to propylthiouracil therapy in intrathoracic goiter. Chest 1981 79(3) 356-7. 

Both goiter and hypothyroidism continue to be reported as complications of lithium therapy (621,622,623). 

In 1989, in 150 patients at different stages of lithium therapy, thyroid function was assessed and subsequently 118 were reassessed at least once and 54 completed a 10-year follow-up (625). The annual rates of new cases of thyroid dysfunction were subclinical hypothyroidism 1.7%, goiter 2.1%, and autoimmunity 1.4%. While these figures were little different from those found in the general population, the authors acknowledged that lithium was a potential cause of thyroid dysfunction. 

Of 42 bipolar patients who had taken lithium for 4-156 months, three had subclinical hypothyroidism, three had subclinical hyperthyroidism, and one was overtly hyperthyroid (623). Ultrasonography showed that goiter was present in 38% and mild thyroid dysfunction was suggested in 48% because of an apparent increased conversion of free T4 to free T3. There was no correlation between the duration of lithium therapy and thyroid abnormalities. 

Euthyroid or hypothyroid goiter can also complicate lithium therapy, although the goiter is seldom of clinical importance and tends to resolve on withdrawal or with thyroxine treatment. In one ultrasound study, there was a... 

After several months of continuous therapy with lithium, diabetes insipidus and goiter may develop. The kidney tubules then become insensitive to the action of antidiuretic hormone, and its administration is ineffective. Either a dose reduction or discontinuation of the lithium corrects this side effect without leaving any residual pathology. In the... 

Levothyroxine has been used in the treatment of nontoxic nodular goiter. In such patients it suppresses TSH secretion, and treatment is given on the assumption that nodular (like normal) thyroid tissue growth is dependent on TSH. The long-term value of levothyroxine in these patients remains unproven, and withdrawal of therapy leads to return of the goitre. Levothyroxine should not be used to treat obesity (see Obesity). 

Thyroid hormones are used either to replace the failing function of the thyroid gland (spontaneous or drug-induced) or to suppress the endocrine function of abnormal thyroid tissues (especially non-toxic struma or goiter or after thyroidectomy for thyroid neoplasms). Although there are abnormalities of the peripheral metabolism of thyroid hormones in some forms of undernutrition or overnutrition, thyroid drug therapy cannot be considered a safe way of treating obesity. 

Despite this variety of clinical findings, frank hypothyroidism and clinical goiter actually are rare sequelae of lithium therapy. However, it is difficult to predict lithium-induced thyroid dysfunction, and regular TRH determinations should be carried out to identify any late-developing disorder (43). 

---