What might replacement of thyroid hormone in a patient with myxedema coma cause?

The replacement of thyroid hormone in a patient with myxedema coma can lead to an adrenal crisis, primarily due to the underlying adrenal insufficiency that can be present in these patients. In cases of severe hypothyroidism, there may also be a concomitant deficiency of cortisol, as both hormones interact in complex ways in the body. The stress of treatment or the physiological changes following the introduction of thyroid hormones can unmask or exacerbate this adrenal insufficiency, leading to an adrenal crisis, which is characterized by severe hypotension, shock, and potential death if not promptly recognized and treated.

In patients with myxedema coma, the importance of assessing adrenal function before initiating thyroid replacement therapy cannot be overstated. Often, it is recommended to perform an adrenal evaluation or initiate glucocorticoids alongside thyroid hormone replacement to mitigate the risk of an adrenal crisis, ensuring the patient's safety during this critical treatment phase.