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thyrotoxicosis

A term that encompasses all forms of thyroid hormone excess, as distinguished from hyperthyroidism that relates specifically to excess thyroid hormone production by the thyroid gland. Etiology: 1) Graves disease 2) toxic multinodular goiter 3) thyroiditis 4) medications - iodine-induced thyrotoxicosis - iodinated contrast - amiodarone [1] - pharmaceutical lithium - interferon-alfa - interleukin-2 - tyrosine kinase inhibitors - immune checkpoint inhibitors 5) thyrotoxicosis facticia: exogenous thyroid hormone - levothyroxine may be found in weight-loss supplements [6] 6) hCG-mediated: pregnancy, trophoblastic disease, germ cell tumor 7) struma ovarii: autonomously functioning thyroid tissue within an ovarian teratoma 8) metastases of follicular thyroid cancer 9) TSH-secreting pituitary adenoma (rare) 10) immune reconstitution inflammatory syndrome Pathology: - excess thyroid hormone production by the thyroid - T3 thyrotoxicosis - thyroiditis resulting in release of preformed thyroid hormone Clinical manifestations: - tachycardia, fine tremor, hyperreflexia, lid lag, proximal muscle weakness - nervousness, anxiety, emotional lability - hyperhidrosis, heat intolerance - palpitations - increased defecation, diarrhea - weight loss - menstrual irregularity - also see hyperthyroidism Laboratory: - decreased or undetectable serum TSH - high serum free T4 &/or serum free T3 - if serum TSH is low, but serum free T4 is normal, high serum free T3 diagnoses T3 toxicosis (rare) [1] - serum thyroglobulin - high with hyperthyroidism & thyroiditis - low with serruptitious thyroid hormone use [1] - thyroid auto-antibodies - anti-thyroid peroxidase Ab - anti-thyroglobulin Ab - TSH receptor Ab in serum & thyroid-stimulating immunoglobulin are associated with Graves disease - elevated erythrocyte sedimentation rate supports diagnosis of thyroiditis Special laboratory: - color-flow doppler ultrasonography distinguishes hyperthyroidism (high flow) from thyroiditis (low flow)* [1] * distinguishes type 1 from type 2 amiodarone-induced thyrotoxicosis [1] * thyroid scintigraphy is test of choice for thyroid nodule(s) with low serum TSH & normal or high serum free T4 [1] * thyroid ultrasound generally not helpful for thyrotoxicosis [5] Radiology: - thyroid scintigraphy - radioactive iodine uptake (iodine-123 uptake) - high with hyperthyroidism & thyroiditis - low with serruptitious thyroid hormone use [1] - radionuclide scanning with iodine-123 or Tc-99m [5] - indicated vs ultrasound if serum TSH is low & serum free T4 is normal or high - contraindicated during pregnancy - not useful if patient has recently received iodinated contrast - diffuse increased uptake in Graves disease - patchy areas of increased uptake with decreased uptake in other areas in toxic multinodular goiter - focal area of increased uptake with decreased uptake in other areas with thyroid adenoma - decreased or no iodine I-123 uptake with - increased iodine load (IV contrast or amiodarone) - thyroiditis during thyrotoxic phase - serruptitious ingestion of thyroid hormona Differential diagnosis: - hyperthyroidism Complications: - increased risk of mild cognitive impairment or dementia in elderly >= 65 years [7] - thyroid storm is a life-threatening form of thyrotoxicosis Management: 1) thyroiditis a) painful inflammatory thyroiditis - non-steroidal anti-inflammatory agents (NSAIDs) - prednisone may be useful - not unless thyroid is tender to palpation (even if ESR elevated) [1] - NOT for infectious thyroiditis b) beta blockers for symptoms of hyperthyroidism 2) prednisone indicated for type 2 amiodarone-induced thyrotoxicosis 3) methimazole + propranolol if contrast-induced thyrotoxicosis [1] - methimazole contraindicated 1st trimester of prognancy & during lactation [1] 4) radioactive I-131 ablation 5) thyroid surgery 3) also see hyperthyroidism

Related

thyroiditis

Specific

factitious hyperthyroidism; factitious thyrotoxicosis; thyrotoxicosis facticia hyperthyroidism T3 thyrotoxicosis thyroid storm

General

endocrine disease sign/symptom

References

  1. Medical Knowledge Self Assessment Program (MKSAP) 15, 16, 18, 19. American College of Physicians, Philadelphia 2009, 2012, 2018, 2022. - Medical Knowledge Self Assessment Program (MKSAP) 19 Board Basics. An Enhancement to MKSAP19. American College of Physicians, Philadelphia 2022
  2. Nayak B, Burman K. Thyrotoxicosis and thyroid storm. Endocrinol Metab Clin North Am. 2006 Dec;35(4):663-86 PMID: 17127140
  3. Vaidya B, Pearce SH. Diagnosis and management of thyrotoxicosis. Review. PMID: 25146390
  4. Bogazzi F, Bartalena L, Martino E. Approach to the patient with amiodarone-induced thyrotoxicosis. J Clin Endocrinol Metab. 2010 Jun;95(6):2529-35. Review. PMID: 20525904
  5. NEJM Knowledge+ Question of the Week. March 8, 2022. https://knowledgeplus.nejm.org/question-of-week/1666/ - Ross DS et al. 2016 American Thyroid Association guidelines for diagnosis and management of hyperthyroidism and other causes of thyrotoxicosis. Thyroid 2016 Oct; 26:1343 PMID: 27521067
  6. NEJM Knowledge+ Endocrinology
  7. Adams R, Oh ES, Yasar S et al Endogenous and Exogenous Thyrotoxicosis and Risk of Incident Cognitive Disorders in Older Adults. JAMA Intern Med. Published online October 23, 2023 PMID: 37870843 PMCID: PMC10594176 (available on 2024-10-23) https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2811088 - Papaleontiou M, Brito JP. Disentangling the association between excess thyroid hormone and cognition in older adults. JAMA Intern Med 2023 Oct 23; [e-pub] PMID: 37870840 https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2811093