Changes in the pituitary-thyroid axis accompanying major affective disorders

Area of Science:

• Endocrinology
• Psychiatry
• Neuroscience

Background:

• Affective disorders are associated with alterations in the hypothalamic-pituitary-thyroid axis.
• Understanding these neuroendocrine changes is crucial for diagnosing and treating mood disorders.

Purpose of the Study:

• To investigate the intercorrelations between the thyrotropin-releasing hormone (TRH) test and peripheral thyroid function in patients with affective disorders.
• To determine the origin of pituitary-thyroid axis dysregulation in mania and depression.

Main Methods:

• Assessed peripheral thyroid function by measuring serum thyroxine (T4), triiodothyronine (T3), T3-uptake, free thyroxine index (FT4I), T3/T4 ratio, and basal and TRH-stimulated thyroid-stimulating hormone (TSH).
• Included 22 manic and 24 depressive patients, with follow-up assessments.
• Measured reverse-T3 (rT3) in a subset of patients.

Main Results:

• Elevated thyroxine levels were observed during acute mania and depression.
• Mania showed increased conversion of T4 to rT3 and decreased inactivation of T4 to T3 compared to depression.
• Both patient groups exhibited an attenuated TSH response to TRH stimulation during florid psychotic episodes.

Conclusions:

• The findings suggest that alterations in the pituitary-thyroid axis during affective psychoses originate from the thyroid gland itself.
• These results indicate a primary thyroidal dysfunction rather than a pituitary-driven mechanism in these mood disorders.