Endocrine Abstracts

Background: While psychiatric disturbances are well-documented manifestations of hypothyroidism, initiation of levothyroxine (LT₄) therapy can also present in a similar manner.

Case: A 34-year-old Filipino with Hashimoto’s thyroiditis consulted for signs and symptoms of hypothyroidism. Thyroid function tests were severely deranged, and an electrocardiogram revealed high grade atrioventricular block. Twenty-four hours after a full replacement dose of LT₄, he developed manic symptoms, which were addressed with sedatives and neuroleptics with gradual restoration of euthymia the following day. He remained stable throughout his admission with no relapse of psychiatric symptoms. A comprehensive workup did not reveal other etiologies for the mania or the heart block. We ultimately attributed the mania to LT₄, and the heart block to hypothyroidism.

Discussion: The temporal relationship between LT₄ intake and onset of mania, plus the lack of other findings on workup, suggest that the mania was probably LT₄-induced. The pathophysiology is thought to be related to abrupt augmentation of catecholamine receptor sensitivity. In the few available case reports, manic symptoms were found to manifest in as short as one day after LT₄ initiation and can likewise resolve the following day. While most cases occurred at higher LT₄ doses, they can also occur at low doses and with gradual dose titration. We gave the full replacement dose for our patient due to his young age, profound hypothyroidism complicated by heart block, and absence of co-morbidities. Our case is significant in the sense that it is the first report involving a double-edged sword: dealing with psychiatric disturbances from LT₄ administration at the same needing to urgently correct severe hypothyroidism with cardiac complications.

Conclusion: Although rare, LT₄ therapy can present with psychiatric disturbances. An exhaustive workup is needed to rule out other diagnoses, and the pros and cons of treatment should be weighed.