This chapter reviews the pathophysiology, clinical manifestations, diagnosis and treatment of hyperthyroidism. Hyperthyroidism has multiple and often dramatic clinical manifestations because thyroid hormones control the basal metabolic rate, affect cardiovascular function by increasing the sensitivity of beta-receptors to catecholamines, and profoundly influence growth, sexual maturation, and n...

Appropriate diagnosis and treatment of hyperthyroidism during pregnancy are of outmost importance, because hyperthyroidism has major adverse impact on both mother and fetus. Since data on the management of thyroid dysfunction during pregnancy is rapidly evolving, two guidelines have been developed by the American Thyroid Association and the Endocrine society in the last 2 years. We compare here...

Thyrotoxicosis is a common disorder, especially in women. The most frequent cause is Graves' disease (autoimmune hyperthyroidism). Other important causes include toxic nodular hyperthyroidism, due to the presence of one or more autonomously functioning thyroid nodules, and thyroiditis caused by inflammation, which results in release of stored hormones. Antithyroid drugs are the usual initial tr...

Hyperthyroidism is recognized as the most common endocrinopathy of older cats. Despite worldwide occurrence, the pathogenesis of feline hyperthyroidism remains unclear. Traditional methods of managing feline hyperthyroidism include thyroidectomy, anti-thyroid medications, and radioactive iodine. Recent studies document that another option now exists for hyperthyroid cats; feeding a limitediodin...

The term subclinical hyperthyroidism describes conditions characterized by a low thyroid-stimulating hormone (TSH) and normal levels of circulating thyroid hormones (thyroxine and triiodothyronine). Subclinical hyperthyroidism has the same causes as overt hyperthyroidism. These include excessive doses of levothyroxine, Graves’ disease, multinodular goiter, and solitary thyroid nodule. Most stud...

Right ventricular papillary muscles from hyperthyroid and normal cats were studied in vitro at 30°C, at contraction frequencies of 12, 30 and 60/min. At 12/min the contractility of hyperthyroid muscles was significantly greater than normal, as indicated by greater velocity of isotonic shortening, isometric tension development, and rate of tension development. Isotonically contracted muscle leng...

The effect of experimental hyperthyroidism, realized by T(4) injection, on central mediators of the hypothalamo-pituitary-interrenal axis (HPI-axis) in common carp (Cyprinus carpio L.) was studied. Our results show that hyperthyroidism evokes a marked 3.2-fold reduction in basal plasma cortisol levels. Corticotropin-releasing hormone-binding protein (CRH-BP) mRNA levels in the hypothalamus, mea...

Hyperthyroidism causes increased energy intake and expenditure, although anorexia and higher weight loss have been reported in elderly individuals with hyperthyroidism. To determine the effect of age on energy homeostasis in response to experimental hyperthyroidism, we administered 200 μg tri-iodothyronine (T3) in 7- and 27-mo-old rats for 14 d. T3 increased energy expenditure (EE) in both the ...

Radionuclide multigated cardiac imaging was performed to assess functional cardiac reserve in patients with hyperthyroidism. In 11 normal individuals, submaximl supine exercise increased heart rate (HR) by 60 percent, systolic blood pressure (BP) by 54 percent, and the left ventricular ejection fraction (LVEF) by 13 percent. All of these increments were statistically significant (p < 0.001). Ei...

Hyperthyroidism has many characteristic manifestations of various organ systems. Cardiovascular effects are frequent in these patients. A less known complication of hyperthyroidism is reversible right-sided heart failure and pulmonary hypertension. In the patient presented, the symptoms of atrial fibrillation and right-sided heart failure were the first manifestations of hyperthyroidism. Dopple...