Euthyroidism

Initial daily doses of 10-40 and 100-600 mg are recommended in clinical practice for MMI and PTU, respectively [1, 2]. Several studies have shown that treatment of hyperthyroidism with single daily doses of 10-40 mg of MMI is effective in the induction of euthyroidism in 80-90% of patients within 6 weeks [2]. The aim of the further antithyroid therapy is to maintain euthyroidism with the lowest necessary diug dose. Intrathyroidal diug accumulation is one cause for the efficiency of a single daily dose regimen. Moreover, a once daily dose yields better patients compliance. Single daily doses of PTU have been shown to be less effective in achieving euthyroidism than administration of three divided doses a day. If a once daily... 

Antithyroid drug treatment 1 year Until euthyroid... 

Treatment with radioiodine or surgery If relapse after 1 year of antithyroid drug treatment After euthyroid ism is achieved... 

Thyroid hormones are used as replacement therapy when the patient is hypothyroid. By supplementing the decreased endogenous thyroid production and secretion with exogenous thyroid hormones, an attempt is made to create a euthyroid (normal thyroid) state Levotliyroxine (Synthroid) is the drug of choice for hypothyroidism because it is relatively inexpensive, requires once-a-day dosages, and lias a more uniform potency than do other thyroid hormone replacement drugs. 

The dosage is individualized to the needs of the patient. The dose of thyroid hormones must be carefully adjusted according to the patient s hormone requirements. At times, several upward or downward dosage adjustments must be made until the optimal therapeutic dosage is reached and the patient becomes euthyroid. 

Once a euthyroid state is achieved, tlie primary health care provider may add a thyroid hormone to tlie therapeutic regimen to prevent or treat hypothyroidism, which may develop slowly during long-term antithyroid drug therapy or after administration of 131I. 

Figure22. (a) Euthyroid(normal)ratmuscleshowingmixtureoftype1 (slow-twitch) and type 2 (fast-twitch) fibers, (b) Hypothyroid rat muscle showing uniformly type 1 (slow-twitch) histochemical profile myofibrillar ATPase after alkaline preincubation.

There are three major goals in the treatment of hypothyroidism replace the missing hormones, relieve symptoms, and achieve a stable biochemical euthyroid state. 

The goals of treating hyperthyroidism are to relieve symptoms, to reduce thyroid hormone production to normal levels and achieve biochemical euthyroidism, and to prevent longterm adverse sequelae. 

Patients receiving LT4 therapy who are not maintained in a euthyroid state are at risk for long-term adverse sequelae. In general, overtreatment and a suppressed TSH is more common than undertreatment27 with an elevated TSH. Patients with long-term overtreatment may be at higher risk for atrial fibrillation and other cardiovascular morbidities, depression, and post-menopausal osteoporosis. Patients who are undertreated are at higher risk for hypercholesterolemia and other cardiovascular problems, depression, and obstetric complications. 

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. 

Antithyroid drugs have a delayed effect. After 2 to 4 weeks of therapy, adjust the dose if the TSH is not in the target range (0.5-2.5 milliunits/L). Once the patient is euthyroid, consider reducing the dose of antithyroid drug to avoid hypothyroidism. 

Desired outcomes include relieving signs and symptoms and achieving a euthyroid state. 

Success of therapy for thyroid disorders must be based not only on short-term improvement of the patient s clinical status and abnormal laboratory values but also on achievement of a long-term euthyroid state. Maintaining the TSH level in the normal range improves symptoms and reduces the risk of long-term complications. 

In the hyperthyroid patient, relieving signs and symptoms and achieving a euthyroid state are the desired outcomes. The method of achieving these outcomes may change over time with the use of antithyroid drugs versus radioactive iodine. 

Euthyroid State of normal thyroid function or hormone activity. 

B12. van den Berghe, G de Zegher, F., and Lauwers, P., Dopamine and the sick euthyroid syndrome in critical illness. Clin. Endocrinol. 41,731-737 (1994). 

D23. Docter, R., Krenning, E. P., de Jong, M., and Hennemann, G., The sick euthyroid syndrome Changes in thyroid hormone serum parameters and hormone metabolism. Clin. Endocrinol. 39, 499-518 (1993). 

Iodine, most ancient of the therapeutic agents for thyroid disorders, inhibits the secretion of thyroid hormone by retarding both the pinocyto-sis of colloid and proteolysis. This effect is observed in euthyroid as well as hyper thyroid persons. 

If thyroidectomy is planned, propylthiouracil (PTU) or methimazole (MMI) is usually given until the patient is biochemically euthyroid (usually 6 to 8 weeks), followed by the addition of iodides (500 mg/day) for 10 to 14 days before surgery to decrease the vascularity of the gland. Levothy-roxine may be added to maintain the euthyroid state while the thiona-mides are continued. 

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