Critical Care Medicine-Endocrine Disorders>>>>>Management During Critical Illness
Question 2#

A 72-year-old woman is admitted to the ICU with hypoxemic respiratory failure and sepsis. Her medical history is notable for hypertension, COPD, and CKD (Cr 1.9). Her vital signs are:

She is intubated, undergoes fluid resuscitation and vasopressor support, and receives broad spectrum antimicrobials and is started on a norepinephrine infusion. In addition to routine laboratory studies a thyroid function panel is sent, which is notable for a T3 of 60 ng/dL (normal 80-180) and a TSH 8 µg/dL (normal 0.5-5).

Based on these laboratory studies, which of the following interventions is most appropriate?

A. No further treatment necessary
B. Send free T4, reverse T3
C. Start IV levothyroxine
D. Start iodine supplementation

Correct Answer is A


Correct Answer: A

This patient presenting with hypoxemic respiratory failure and sepsis has a nonthyroidal illness syndrome (NTIS), which had previously been called the euthyroid sick syndrome. NTIS, which was previously called the euthyroid sick syndrome, is characterized by low T3, usually elevated reverse T3, normal or low TSH, and if prolonged, low T4 levels in clinically euthyroid patients experiencing critical illness (trauma, sepsis, DKA, CKD, malnutrition). A variety of mechanisms have been proposed to explain these thyroid hormone abnormalities, including decreased conversion of T4 to T3, decreased binding to thyroid-binding globulin, and the effect of circulating cytokines and oxidative stress.

Diagnosis of primary hypothyroidism can be difficult in patients who are severely ill and not known to have hypothyroidism before admission to the ICU because serum thyroid hormones, especially T3 , are decreased in most patients in the ICU because of NTIS. In patients clinically suspected to have severe hypothyroidism, the most useful test for diagnosis is measurement of plasma TSH, because a normal plasma TSH excludes primary hypothyroidism. In patients with a combination of primary hypothyroidism and NTIS, serum TSH concentration is still high and responsive to levothyroxine treatment. However, of note is that in patients who have hypothyroidism the high serum TSH concentration might decrease during the acute phase of illness especially if dopamine or high doses of glucocorticoids are given. Thus, high serum TSH in combination with low serum T4 is indicative of hypothyroidism.


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