Answer

Pathophysiology of Thyrotoxicosis

Introduction

                Thyrotoxicosis is described as a clinical disorder that develops as a result of excess thyroid hormone activity. Typically the condition is due to high circulating levels of thyroid hormones. These hormones include T3 and/or T4. The disease is often used incorrectly used interchangeably with hyperthyroidism. Hyperthyroidism is just a form of thyrotoxicosis which develops as a result of excessive production of the endogenous thyroid hormone. It can result in development of series complications when not diagnosed in time and managed appropriately. Complications include congestive heart failure, altered mental status, delirium, atrial fibrillation, muscle weakness, cardiovascular collapse, thromboembolic disease, and death (Blick, Nguyen, & Jialal, 2021).

                The prevalence of the disease in the U.S. is 1.2%, including 0.7% subclinical cases and 0.5% overt thyrotoxicosis. The incidence tend to peak in people aged between 20 and 50 years. The incidence of Graves’ disease, the leading cause of thyrotoxicosis, is 20-50 cases per 100,000 population followed by toxic multi-nodular goiter and toxic adenoma. Women aged 30 to 50 years are mostly affected by the Graves’ disease. The incidences of toxic nodular goiter tend to increase with age as well as in iodine-deficient regions (Blick et al., 2021). 

Causes

                Thyrotoxicosis has many causes and identification of the correct etiology in a case is important for proper management of the condition. The causes of thyrotoxicosis can be classified into exogenous and endogenous causes. Exogenous causes include excessive replacement therapy with the use of levothyroxine and factitious hyperthyroidism. Endogenous causes include toxic multi-nodular goiter, toxic adenoma, Graves’ disease, TSH-producing adenoma or pituitary adenoma, drug-induced, HCG-mediated hyperthyroidism, and thyroiditis. Graves’ disease is the leading cause of thyrotoxicosis then followed by toxic multi-nodular goiter and toxic adenoma (Blick et al., 2021).

Symptoms

                 The clinical presentation of thyrotoxicosis tends to vary from one person to the other. It can range from asymptomatic to development of a fatal thyroid storm. Symptoms of the disease are associated with excess thyroid hormone induced hyper-metabolic state. They include weight loss, palpitations, and heat intolerance (Blick et al., 2021).  Other common manifestations include atrial fibrillation, tremors, fatigue, and goiter (Sharma & Stan, 2019).

Dietary and Lifestyle Changes

                A low iodine diet is recommended for management of hyperthyroidism. A low iodine diet should be followed before a patient goes through radiation therapy to remove damaged or excess thyroid cells.  Dietary changes include use of non-iodized salt, tea or coffee without dairy or milk or soy-based creamers, fresh or canned fruit, egg whites, unsalted nuts and nut butters, bread made without salt, potatoes, oats, maple syrup, and honey.  Eating of cruciferous vegetables can help stop the thyroid from utilizing iodine properly. These vegetables include bamboo shoots, broccoli, bok choy, Brussels sprouts, cassava, cauliflower, collard, kale, mustard, rutabaga, and kale. Minerals such as iron, selenium, zinc, vitamin D, and calcium are essential for helping the thyroid to balance thyroid hormone production (Iftikhar, 2019). Strategies for management of Graves’ disease include eating healthy diets and exercising and easing of stress. Exercise in necessary to prevent one from gaining extra weight after the etiological cause of thyrotoxicosis has been corrected. Stress may worsen or trigger Graves’ disease (MayoClinic, 2021). Other lifestyle changes include smoking cessation and wearing sunglasses if the eyes protrude (MayoClinic, 2021).

Treatment Options

                Treatment of thyrotoxicosis is determined by the underlying cause. Use of beta-blockers such as propranolol is indicated for reduction of adrenergic clinical presentations such as sweating, tachycardia, and anxiety. There are three mainstay treatment approaches for thyrotoxicosis: radioiodine, thionamide drugs, and thyroid surgery. Thionamide medications include methimazole and propylthiouracil, which reduce production of thyroid hormone by functioning as preferential-substrates for thyroid peroxidase. In high doses, propylthiouracil can reduce peripheral conversion of T4 to T3 (Blick et al., 2021).

                In management of Graves’ disease, methimazole (15mg to 30mg per day for 4 – 8 weeks) is used. After this period most patients tend to become euthyroid. Thionamide can then be used to block the production of thyroid hormone. Levothyroxine is used to maintain a state of euthyroidism.  Radioiodine therapy is the most common therapeutic approach for management of Graves’ disease among adults in the U.S. Radioiodine therapy can also be used to treat toxic nodules and toxic multi-nodular goiter. Radioiodine is administered as a single oral dose. Radioiodine can induce tissue-specific inflammation resulting in fibrosis and thyroid tissue destruction over a period of 6 to 12 months. Most patients who receive radioiodine are indicated for a life-long levothyroxine treatment (Blick et al., 2021).

                Partial of total thyroidectomy is an effective and rapid method of treating thyrotoxicosis. After the procedure, the patient should rely on levothyroxine therapy.  Possible complications of thyroidectomy include vocal cord paresis as a result of the damage to recurrent laryngeal nerve and hypocalcemia as a result of hypothyroidism (Blick et al., 2021).

Conclusion

                Thyrotoxicosis is a complex disorder with multiple etiologies. Identification of a correct etiology is necessary for identification of appropriate treatment. The disease is characterized by high levels of circulating thyroid hormone. Symptoms include weight loss, palpitations, heat intolerance, atrial fibrillation, tremors, fatigue, and goiter. There are dietary and lifestyle changes (as discussed above) that can support realization of better outcomes in management of the condition. Treatment approaches for thyrotoxicosis include radioiodine therapy, pharmacotherapy, and partial or total thyroidectomy.