Clinical Case: Sick euthyroid syndrome

A 57 yo female was admitted to the hospital with multilobar pneumonia.

On hospital day 2, thyroid function tests showed low levels of TSH, T4 and T3.

What is the most likely diagnosis?

Read more in Sick euthyroid syndrome in a patient with multilobar pneumonia on ClinicalCases.org.

Image source: Thyroid histology, Wikipedia, public domain.