Medications and Thyroid Function

OVERVIEW

Many medications have effects on thyroid function, through multiple mechanisms:

  • altered TSH secretion from the pituitary gland
  • altered thyroid hormone secretion from the thyroid gland
  • altered T3 and T4 transport in the serum
  • altered T3 and T4 metabolism peripherally
  • immune reconstitution
  • tyrosine kinase inhibtion

EXAMPLES

Alter TSH secretion from the pituitary gland

  • Increase TSH: opioids
  • Inhibits TSH release: glucocorticoids, dopamine, octreotide
  • Bexarotene suppresses pituitary TSH-β promoter

Alter thyroid hormone secretion from the thyroid gland

  • Decrease thyroid hormone synthesis: propylthiouracil, methimazole
  • Decrease thyroid hormone secretion: iodide (Wolff-Chaikoff effect occurs over 7-10 days), amiodarone, lithium, Lugol’s solution
  • Increase thyroid hormone secretion: iodide (escape from the Wolff-Chaikoff effect or the Jod-Basedow phenomenon occurs long-term), amiodarone

Decreased exogenous T4 absorption from the GI tract

  • Cholesystramine, colestipol, sucralfate, ferrous sulfate, aluminum hydroxide, omeprazole

Alter T4 and T3 transport in serum

  • Increase serum TBG: estrogens, heroin, methadone, mitotane, fluorouracil
  • Decrease serum TBG: androgens, anabolic steroids
  • Displacement from protein-binding sites: furosemide, salicylates, phenytoin, carbamazepine, meclofenamate, heparin

Alter T4 and T3 metabolism peripherally

  • Increase hepatic metabolism: phenobarbital, phenytoin, carbamazepine and rifampin
  • 5’-monodeiodinase inhibition (blocks metabolism of T4 to T3): glucocorticoids, propanolol, propylthiouracil, amiodarone, cytokines (e.g. IFN alpha)

Immune reconstitution

  • Alemtuzumab

Hypothyroidism (tyrosine kinase inhibitors)

  • Sunitinib: ? destructive thyroiditis,? blockade of iodine uptake,? inhibition of peroxidase activity
  • Imatinib: ? induction of uridine diphosphate-glucuronosylotransferases (UGTs)

References and Links

  • Kundra P, Burman KD. The effect of medications on thyroid function tests. Med Clin North Am. 2012 Mar;96(2):283-95. PMID: 22443976.

CCC 700 6

Critical Care

Compendium

Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also the Innovation Lead for the Australian Centre for Health Innovation at Alfred Health, a Clinical Adjunct Associate Professor at Monash University, and the Chair of the Australian and New Zealand Intensive Care Society (ANZICS) Education Committee. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of two amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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