Thyroid Function Testing in Hospitalized Patients: A Practical Framework for Clinicians

Area of Science:

• Endocrinology
• Internal Medicine
• Clinical Physiology

Background:

• Thyroid-stimulating hormone (TSH) is the standard outpatient screening test for thyroid dysfunction.
• Hospitalized patients present unique challenges in thyroid function test interpretation due to acute illness, medications, and assay interference.
• Non-thyroidal illness syndrome (euthyroid sick syndrome) is prevalent in critically ill patients, causing transient thyroid hormone level alterations.

Purpose of the Study:

• To review the physiology of thyroid hormone action and hypothalamic-pituitary-thyroid axis regulation in the hospital setting.
• To summarize the presentation and management of thyroid emergencies.
• To provide guidance on interpreting thyroid function tests in hospitalized patients and identify scenarios requiring endocrinology consultation.

Main Methods:

• Narrative review of thyroid hormone physiology and clinical presentations.
• Summary of current literature on thyroid function testing in hospitalized patients.
• Development of a diagnostic algorithm for inpatient thyroid evaluation.

Main Results:

• Acute illness and other factors can significantly alter thyroid function tests in hospitalized patients, mimicking primary thyroid disorders.
• Understanding the dynamic changes in the hypothalamic-pituitary-thyroid axis is crucial for accurate diagnosis.
• Thyroid emergencies require specific management strategies.

Conclusions:

• Distinguishing transient thyroid function abnormalities from true thyroid disease in hospitalized patients is essential for appropriate management.
• A practical diagnostic algorithm can aid clinicians in evaluating thyroid function in the inpatient setting.
• Endocrinology consultation is valuable in complex cases and thyroid emergencies.