Ablation, thyroid

Etiology 1) Primary hypothyroidism - surgery, radioiodine ablation, thyroiditis. 2) Secondary hypothyroidism - hypofunction of pituitary or hypothalamus. 

Often the amount of administered radioactivity has been used as the criterion to determine whether a patient should be hospitalized or not. T-treated patients, however, do not have the same iodine kinetics. The clearance of from ablated thyroid cancer patients is much faster than from patients treated for hyperthyroidism. The calculations by Coover et al. (2000) enable the nuclear medicine physician to determine the maximum dose to be prescribed to each individual patient. There is a wide... 

Low dose (30mCi) successfully ablates thyroid remnant in 10—77% of cases (Table 103.1). 

Patients with cardiac disease and elderly patients are often treated with thionamides prior to RAI ablation because thyroid hormone levels will transiently increase after RAI treatment due to release of preformed thyroid hormone. 

The Class III effects of amiodarone develop over several weeks. This time-course is similar to that seen in thyroid gland ablation [25]. It is well known that patients with hypothyroidism have long QT intervals which are indicative of prolonged action potentials. Amiodarone has been shown to inhibit the conversion of thyroxine (T4) to triiodothyronine (T3) both in human subjects [26] and in vitro [27]. It has been argued that the Class III effects of amiodarone are due to its effects on thyroid hormones [28]. Others, however, argue that there is no relationship between prolongation of ventricular refractory period by amiodarone and thyroid state [29]. 

Milhcurie amounts of (lodotope 1-131) are used for thyroid ablation in the management of hyperthyroidism. is taken up and trapped in the same manner... 

Hypothyroidism, a condition in which the circulating concentrations of thyroid hormones are too low, is the most prevalent thyroid disease. Primary hypothyroidism, the commonest form, is an autoimmune disease (Hashimoto s thyroiditis) often associated with goitre. Like other autoimmune diseases, it is more prevalent in women (4 per 1000) than in men (1 per 1000). Other causes include thyroidectomy, radioac tive ablation and, in some countries, iodine deficiency. Hypothyroidism can also be caused by several drugs, including lithium, interleukin-2 and interferon. Secondary hypothyroidism is a disease caused by decreased secretion of TSH by the pituitary. 

The management of hyperthyroidism due to amiodarone has been reviewed in the light of the practices of 101 European endocrinologists (60). Most (82%) treat type I amiodarone-induced hyperthyroidism with thionamides, either alone (51%) or in combination with potassium perchlorate (31%) the preferred treatment for type II hyperthyroidism is a glucocorticoid (46%). Some initially treat all cases, before the type has been established, with a combination of thionamides and glucocorticoids. After restoration of normal thyroid function, 34% recommend ablative therapy in type I hyperthyroidism and only 8% in type II. If amiodarone therapy needs to be restarted, 65% recommend prophylactic thyroid ablation in type I hyperthyroidism and 70% recommend a wait-and-see strategy in type II. 

Hermida JS, Tcheng E, Jarry G, Moullart V, Arlot S, Rey JL, Delonca J, Schvartz C. Radioiodine ablation of the thyroid to prevent recurrence of amiodarone-induced thyrotoxicosis in patients with resistant tachyarrhythmias. Europace 2004 6(2) 169-74. 

J. P. Stroraasli, E. L. Schoeniger, H. K. Hellerstein, H. L. Friedell, Thyroid ablation with I131 in euthyroid cardiac patients with special reference to preparation with antithyroid drugs, Radiology 4, El0-21 (1960). 

Ptacek Again, those are pretty rare. The patients are thyrotoxic and they have paralysis just like the hypokalaemics, except that when you ablate their thyroid, the thyrotoxic periodic paralysis resolves. There was one small family reported. I believe that this is a hereditary disorder, but we don t see it as a hereditary disorder much because it is a predisposing mutation and you also have to be thyrotoxic for the paralysis to manifest. We ve looked for Ca channel mutations in those patients but haven t found any. 

In widely metastatic follicular carcinomas with relatively well-preserved function, sufficient thyroid hormone can he synthesized and secreted to produce thyrotoxicosis. In most instances, a previous diagnosis of thyroid mahgnancy has been made. The diagnosis can be confirmed by whole-body scanning. Treatment with I is generally effective at ablating functioning thyroid metastases. 

Tallstedt L, Lundell G. Radioiodine treatment, ablation, and ophthalmopathy A balanced perspective. Thyroid 1997 7 241-245. 

We have shown that plasma B, levels may be elevated in over 50% of patients with thyrotoxicosis (B22). In addition, when patients are rendered euthyroid by I-thyroid ablation, plasma B, levels return to within reference limits. In contrast, we found that thyrotoxic patients that were rendered euthyroid with carbimazole had B concentrations that fell significantly from pretreatment levels but not to... 

A considerable advance in the management of thyroid cancer has resulted from the introduction of recombinant human TSH (thyrogen). A dose of 0.9 mg is administered intramuscularly, followed by an identical dose 24 hours later. The serum thyroglobuLin is then measured 48-72 hours after the second TSH injection this has become the preferred diagnostic test for following patients with differentiated thyroid cancer who have had thyroidectomy and ablation of any remnant tissue with radioactive iodine. This regimen can also be used to stimulate iodine uptake by malignant cells in a total body scan (see below). 

The most severe form (f hyperthyroidism is thyroid storm, a rare but life-threatening disease that usually is precipitated by an intercurrent medical problem. Precipitating factors include infections, stress, trauma, thyroidal or nonthyroidal surgery, diabetic ketoacidosis, labor, heart disease, and rarely, radioactive iodine ablation. Clinical features are similar to those of thyrotoxicosis, but are more severe. Cardinal features include fever and tachycardia out of proportion to the fever. Nausea, vomiting, diarrhea, agitation, and confusion are frequent presentations. The abnormalities in TFTs are not necessarily worse than those in uncomplicated thyrotoxicosis and thyroid storm is a clinical diagnosis. 

Thyroid Hypofunction Hypothyroidism is the most common disorder of thyroid function. It can be divided into patients who have a failure of the thyroid gland to produce sufficient thyroid hormone (primary hypothyroidism) and patients in which pituitary or hypothalamic disease is associated with impaired TSH stimulation (central or secondary hypothyroidism). Worldwide, primary hypothyroidism is caused most often by iodine deficiency. In areas where iodine is sufficient, chronic autoimmune thyroiditis (Hashimoto s thyroiditis) accounts for most cases. Other causes include postpartum thyroiditis, surgical removal, or radioactive iodine ablation of the gland. Hypothyroidism present at birth (cretinism) is the most common preventable cause of mental retardation in the world. 

Radioactive iodine ablation therapy for hyperthyroidism is relatively inexpensive, does not require hospitalization, and is relatively free of adverse effects. It is associated with a high incidence of permanent hypothyroidism, and all patients must be warned of this and followed therecffer for the onset of hypothyroidism. Because thyroid hormone replacement therapy is generally well accepted by the patient, many specialists prefer to treat with relatively higher doses to rapidly... 

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