Patients diagnosed with thyroid disease often use it as an explanation or excuse for neuropsychiatric symptoms; this is a form of "labeling effect."
Thyroid dysfunction causes many well-recognized changes at the level of the brain, most of which are reversible with treatment. The August issue of Current Opinion in Endocrinology, Diabetes, and Obesity has published a review that summarizes hypothoroidism’s neuropsychiatric effects. It also provides guidelines for diagnosing these comorbidities and when to treat.
Overt hypothyroidism (an elevated serum thyroid-stimulating hormone [TSH] level with a low free thyroxine level) is renowned for its lethargy, hyporeflexia, and poor motor coordination. Subclinical hypothyroidism (an elevated TSH with a normal free thyroxine) seems to cause some subtle memory impairment. Patients who have hypothyroidism often have other neuropsychiatric comorbidities: affective disorders, depression, cognitive function loss, anxiety, or irritability.
Author Mary H. Samuels, MD, stresses that subclinical hypothyroidism has not been shown to cause major neuropsychiatric deficits, but confirms that small deficits in memory and executive function are possible. Patients diagnosed with thyroid disease often use it as an explanation or excuse for neuropsychiatric symptoms; this is a form of “labeling effect.” She notes that euthyroid patients, educated through the media and unreliable sources about hypothyroidism’s effects, may request thyroid supplementation if they experience fatigue, mood changes, or memory deficits.
Patients who have thyroid disease and are adequately treated with levothyroxine should be referred for additional evaluation and therapy if neuropsychiatric symptoms continue. Increasing levothyroxine doses or prescribing other forms of thyroid hormone is not recommended.
Samuels concludes with a summary reminding clinicians that patients who have hypothyroidism-induced neuropsychiatric symptoms will usually improve with levothyroxine. Although, in rare cases, the improvements may not lead to complete symptom resolutions.
In patients with subclinical hypothyroidism, clinicians need to set realistic expectations about symptom etiology and reversibility with treatment.