Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content +++ KEY FEATURES +++ ESSENTIALS OF DIAGNOSIS ++ Hyperreflexia, tremor Low (suppressed) thyroid-stimulating hormone (TSH) levels (below the lower limit of normal) High free T4, total T4, and free thyroxine index, and/or high free T3 or total T3 radioimmunoassay High 24-hour radioactive iodine uptake in Graves’ disease or toxic multinodular goiter; low uptake in thyroiditis or exogenous cause. Goiter (often with a bruit) and exophthalmos in Graves’ disease +++ GENERAL CONSIDERATIONS ++ Hyperthyroidism increases levels of T3, which enhances myocardial systolic and diastolic function Beta catecholamine receptor responsiveness is increased, also leading to effects mimicking sympathetic nervous system activation such as increased heart rate Although cardiac performance is augmented, the heart functions at near capacity in hyperthyroidism, with little reserve Hyperthyroidism can be caused by: – Diseases of the thyroid gland such as Graves’ disease – Exogenous agents such as amiodarone – Rare thyroid hormone–producing tumors such as struma ovarii In apathetic hyperthyroidism of the elderly, atrial fibrillation may be the only manifestation +++ CLINICAL PRESENTATION +++ SYMPTOMS AND SIGNS ++ Weight loss despite increased appetite Nervousness, anxiety, insomnia Heat intolerance, diaphoresis, diarrhea Proximal muscle weakness Palpitations, dyspnea, chest pain +++ PHYSICAL EXAM FINDINGS ++ Stare, lid retraction and lag Exophthalmos in Graves’ disease Goiter Tachycardia, loud heart sounds, flow murmurs Hyperreflexia Pretibial myxedema +++ DIFFERENTIAL DIAGNOSIS ++ Anxiety disorder Factitious or iatrogenic thyrotoxicosis Angina, atrial fibrillation, and other signs without thyrotoxicosis +++ DIAGNOSTIC EVALUATION +++ LABORATORY TESTS ++ Reduced TSH, elevated free T4 and T3 +++ ELECTROCARDIOGRAPHY ++ Sinus tachycardia in many Atrial fibrillation in some +++ IMAGING STUDIES ++ Echocardiography: – Hypercontractile state – Left ventricular hypertrophy – Left atrial enlargement in some patients +++ DIAGNOSTIC PROCEDURES ++ Radioactive iodine thyroid uptake may be increased or decreased, depending on the cause of hyperthyroidism +++ TREATMENT +++ CARDIOLOGY REFERRAL ++ Atrial fibrillation Heart failure Acute coronary syndromes +++ HOSPITALIZATION CRITERIA ++ Atrial fibrillation Heart failure Acute coronary syndromes +++ MEDICATIONS ++ Beta blockers to reduce heart rate and improve symptoms – Propranolol is preferred because it blocks peripheral conversion of T4 to T3 Thionamides to block thyroid hormone release and prevent synthesis +++ THERAPEUTIC PROCEDURES ++ Radioactive iodine ablation +++ SURGERY ++ Subtotal thyroidectomy in selected cases +++ MONITORING ++ ECG monitoring in hospital as appropriate TSH monitoring during treatment ... Your Access profile is currently affiliated with '[InstitutionA]' and is in the process of switching affiliations to '[InstitutionB]'. Please click ‘Continue’ to continue the affiliation switch, otherwise click ‘Cancel’ to cancel signing in. Get Free Access Through Your Institution Learn how to see if your library subscribes to McGraw Hill Medical products. Subscribe: Institutional or Individual Sign In Username Error: Please enter User Name Password Error: Please enter Password Forgot Password? Forgot Username? Sign in via OpenAthens Sign in via Shibboleth You already have access! Please proceed to your institution's subscription. Create a free a profile for additional features.