Diagnosis of hyperthyroidism when serum-thyroxine alone is raised

Area of Science:

• Endocrinology
• Internal Medicine
• Thyroidology

Background:

• Patients with non-thyroidal diseases can present with altered thyroid hormone levels.
• Distinguishing true hyperthyroidism from other causes of thyroid dysfunction is clinically important.

Purpose of the Study:

• To investigate the significance of elevated total and free thyroxine (T4) with normal triiodothyronine (T3) in hospitalized patients with intercurrent illnesses.
• To differentiate between true hyperthyroidism and other causes of altered thyroid hormone levels in this patient population.

Main Methods:

• Study included 31 patients admitted with non-thyroidal intercurrent diseases and elevated serum T4/free T4 with normal T3.
• Patients were categorized into three groups based on clinical course and laboratory findings.
• Analysis of clinical outcomes, including development of hyperthyroidism and response to iodine-containing preparations.

Main Results:

• 14 patients developed classic hyperthyroidism post-recovery; 11 had received iodine.
• 11 patients showed normalization of serum T4 with recovery from illness.
• 6 patients maintained elevated serum T4 post-recovery, including 2 with transient iodine-induced hyperthyroidism (Jod-Basedow).

Conclusions:

• Elevated T4 with normal T3 in patients with systemic illness does not always signify hyperthyroidism.
• Changes in peripheral T4 metabolism likely contribute to these laboratory findings.
• Clinical follow-up is essential for early detection and management of hyperthyroidism in patients with elevated T4 and normal T3.