Hyperthyroidism
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Contents |
More Specific Terms
- factitious hyperthyroidism
- hashitoxicosis
- selective pituitary thyroid hormone resistance (PRTH); familial hyperthyroidism due to inappropriate thyrotropin secretion
- subacute lymphocytic thyroiditis
- subclinical hyperthyroidism
- thyroid storm
- thyrotoxic hypokalemic periodic paralysis
- toxic multinodular goiter (Plummer's disease)
Etiology
- Graves' disease (most common cause)
- toxic multinodular goiter
- most common cause in older patients
- iodine from contrast agents or amiodarone can precipitate thyrotoxicosis
- iodide-induced (uncommon, transient) i.e. amiodarone, contrast agents
- thyroid adenoma (uncommon)
- hyperfunctioning thyroid carcinoma, esp. metastatic
- postpartum (uncommon, transient)
- subacute thyroiditis (uncommon, transient)
- factitious or iatrogenic exogenous T4
- choriocarcinoma or hydatidiform mole
- chorionic gonadotropin
- TSH-like molecule
- struma ovarii ( ovarian teratomatous thyroid)
- neonatal hyperthyroidism due to maternal Graves' disease
- TSH- secreting pituitary tumor
- hypersecretion of hypothalamic TRH
- genetic defects in thyrotropin receptor ( TSHR)
Pathology
-
- increased heart rate
- increased stroke volume
- increased cardiac output
- decreased peripheral vascular resistance
- widened pulse pressure
- cardiomegaly
- atrophy & fatty infiltration of skeletal muscle
- focal interstitial lymphocytic infiltration
- minimal fatty changes in liver
- osteoporosis
- generalized lymphoid hyperplasia & lymphadenopathy
Genetics
- may be associated with defects in thyrotropin receptor ( TSHR)
Clinical-manifestations
- Symptoms:
- alertness, emotional lability, irritability, nervousness, proximal muscle weakness, palpitations, hyperphagia, weight loss, diarrhea, heat intolerance, dyspnea, arthralgias, menstrual irregularity
- hyperkinesia, rapid speech, quadriceps weakness, fine tremor, abundant fine hair, moist skin, increased sweating, onycholysis, lid lag, stare, chemosis, periorbital edema, proptosis, extraocular muscle palsy, accentuated heart sound, tachycardia, atrial fibrillation, wide pulse pressure, systolic ejection murmur, bounding pulse, forceful apical pulse, goiter, pretibial myxedema, vitiligo
- Elderly patients:
- sympathetic manifestations may be absent
- may present only with weight loss, anorexia, CHF, palpitations or atrial fibrillation
Laboratory
- increased total serum T4, free T4, T4 index
- increased total T3 or free T3 if serum T4 is normal ( T3 toxicosis)
- suppressed serum TSH (primary hyperthyroidism)
- elevated serum TSH, serum T4 & free T3 suggest TSH- secreting pituitary tumor
- low serum TSH; normal serum T4 & free T3 suggest subclinical hyperthyroidism
- thyroid-stimulating immunoglobulin ( TSI)
- anti-thyroid peroxidase autoantibody identifies Hashimoto's thyroiditis
- elevated serum thyroglobulin & ESR distinguish thyroiditis from serreptitious ingestion of thyroxine (suppressed serum thyroglobulin & normal ESR)
Diagnostic-procedures
- color-flow doppler ultrasonography distinguishes hyperthyroidism (high flow) from thyroiditis (low flow) [4]
Radiology
- thyroid scan ( radioactive iodine uptake)
- propylthiouracil, methimazole & iodides interfere, stop at least 1 week prior to scan; propranolol is OK
- radioactive iodine uptake is increased in
- radioactive iodine uptake is suppressed in
-
- factitious hyperthyroidism
- recent iodine load ( contrast)
- 99m- Tc-pertechnate scan ( technesium scan) identifies
- autonomously functioning thyroid nodule or
- multinodular goiter
Complications
- thyroid storm is severe life-threatening hyperthyroidism
Differential-diagnosis
Management
- see thyroid storm, severe life-threatening hyperthyroidism
- radioactive iodine I[131] ablation
- 100 to 200 uCi/g of tissue
- maximal effect in 2-3 months
- hypothyroidism eventually occurs in 80% of patients
- thyroid hormone replacement as needed
- exacerbation of ophthalmopathy (controversial)
- subtotal thyroidectomy
- pharmacologic
- thionamides -inhibit thyroid hormone synthesis
- methimazole 15 mg QD or BID [5]
- preparation for thyroidectomy
- severe Graves disease ophthalmopathy
- reluctance to take radioiodine
- methimazole better than propylthiouracil except during pregnancy [5]
- propranolol 20-40 mg PO QID
- control of palpitations, tremor, anxiety
- also inhibits peripheral T4 -> T3 conversion
- iodide inhibits release of hormone from thyroid gland
- saturated solution of KI ( SSKI)
- Lugol's solution
- other iodide-containing agents
- sodium ipodate ( Oragrafin)
- iopanoic acid ( Telepaque)
- these agents also inhibit T4 -> T3 conversion
- NSAIDs or glucocorticoids for painful thyroiditis [3]
- treat depression if present in apathetic variant of hyperthyroidism [4]
- anticoagulation prior to cardioversion if associated with atrial fibrillation
More General Terms
Additional Terms
- Graves disease (Basedow's disease, exothalmic goiter)
- methimazole; thiamazole (Tapazole)
- propranolol (Inderal, InnoPran)
- propylthiouracil (PTU)
- thyroidectomy
- toxic multinodular goiter (Plummer's disease)
Internet Database
OMIM: 145650
OMIM: 603372
OMIM: 603373
OMIM: 609152
References
- DeGowin & DeGowin's Diagnostic Examination, 6th edition, RL DeGowin, McGraw Hill, New York 1994
- Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 54, 205
- Medical Knowledge Self Assessment Program (MKSAP) 11, 14, 15 American College of Physicians, Philadelphia 1998, 2006, 2009
- Solomon DH, in: UCLA Intensive Course in Geriatric Medicine & Board Review, Marina Del Ray, CA, Sept 12-15, 2001
- Nakamura H, Noh JY, Itoh K, Fukata S, Miyauchi A, Hamada N. Comparison of methimazole and propylthiouracil in patients with hyperthyroidism caused by graves' disease. J Clin Endocrinol Metab. 2007 Jun;92(6):2157-62. Epub 2007 Mar 27. PMID: [1]
- Bahn Chair RS et al Hyperthyroidism and other causes of thyrotoxicosis: management guidelines of the American Thyroid Association and American Association of Clinical Endocrinologists. Thyroid. 2011 Jun;21(6):593-646 PMID: [2]
