Active thyroid gland linked to depression in elderly

Even a slightly active thyroid gland - including one considered in the normal range - may be enough to trigger depression in older people, a new study suggests.

To determine a thyroid gland's activity level, the researchers measured levels of thyroid-stimulating hormone (TSH) in 1,503 people with an average age of 70. Based on their amount of TSH secretion, the participants were classified into three groups, with a low TSH level indicating the thyroid gland is more active and producing the needed thyroid hormones.

A questionnaire was also given in order to assess symptoms of depression. Those who exhibited signs of depression during this first visit were excluded from the study.

The participants were then observed during the next eight or so years, during which the development of depressive symptoms were assessed along with TSH levels.

The researchers found that study participants with TSH levels slightly above the normal range reported more depressive symptoms as time went on.

"We found that older individuals with thyroid activity at the high end of the normal range had a substantially increased risk of developing depression over the course of an eight-year period compared to individuals who had less thyroid activity within the normal range," Marco Medici, one of the senior study authors, said in a press release. "This suggests that people with even minor changes in thyroid function may experience similar mental health effects as those with overt thyroid disorders, including hypothyroidism and hyperthyroidism."

According to the researchers, the study could help blaze new paths to recognizing and dealing with depression.

"These results provide insight into the powerful effects thyroid activity can have on emotions and mental health," Medici said. "This information could influence the process of diagnosing and treating depression, as well as treatments for individuals with thyroid conditions."