Respirology/ ICU

How Does Hypothyroidism Cause Hypoventilation?

Although rare, the differential diagnosis of hypoventilation and hypercapnia respiratory failure includes hypothyroidism. It is usually associated with severe hypothyroidism (i.e. myxedema coma) [1].

The suspected mechanism(s) by which hypothyroidism causes hypoventilation are:

  1. Depression of the central ventilatory drive response to hypercapnia/hypoxia [2].
  2. Skeletal muscle myopathy with a weakening of the diaphragm and intercostal muscles [3-4].

Typically, the introduction of levothyroxine [T4] supplementation will reverse the underlying pathology [5-6].

Img Credit: E.H. Schlenker / Respiratory Physiology & Neurobiology 181 (2012) 123– 131. Fig 1. Models comparing effects of euthyroidism (a) and hypothyroidism (b) on the respiratory system. Hypothyroidism impacts the function of CNS, and the innervation and function of the upper airways, tongue, and respiratory muscles. Other alterations that occur with hypothyroidism include abnormalities in the development and function of the lungs, carotid and aortic bodies, CO2 CNS sensors and the afferent information from these regions to regulate breathing. Mechanisms responsible for these changes are not clearly understood and are represented by the question marks.

References:

  1. NORDQVIST P, DHUNER KG, STENBERG K, ORNDAHL G. Myxoedema coma and carbon dioxide-retention. Acta Med Scand. 1960 Mar 10;166:189-94.
  2. Duranti R, Gheri RG, Gorini M, et al. Control of breathing in patients with severe hypothyroidism. Am. J. Med. 1993;95:29–37.
  3. Siafakas NM, Salesiotou V, Filaditaki V, Tzanakis N, Thalassinos N, Bouros D. Respiratory muscle strength in hypothyroidism. Chest. 1992 Jul;102(1):189-94.
  4. Schlenker EH. Effects of hypothyroidism on the respiratory system and control of breathing: Human studies and animal models. Respir Physiol Neurobiol. 2012 Apr 30;181(2):123-31.
  5. Ladenson PW, Goldenheim PD, Ridgway EC. Prediction and reversal of blunted ventilatory responsiveness in patients with hypothyroidism. Am J Med. 1988 May;84(5):877-83.
  6. Behnia M, Clay AS, Farber MO. Management of myxedematous respiratory failure: review of ventilation and weaning principles. Am. J. Med. Sci. 2000;320:368–373.
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Dr. C Humphreys

Internal Medicine

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Dr. C Humphreys

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