Mild Thyroid Dysfunction Does Not Lead to Depression

Study Highlights Need to Reconsider Routine Thyroid Screening

Deborah Brauser

September 02, 2011

September 2, 2011 — Subclinical thyroid disease is unlikely to be associated with incident or prevalent depression in older men, suggesting that routine screening for thyroid dysfunction in this population is unnecessary, new research suggests.

The Health in Men Study assessed almost 4000 Australian men older than 65 years who were free of overt thyroid disease and showed that serum concentrations of both thyroid-stimulating hormone and free thyroxine did not affect the odds of developing depression up to 5 years later.

Subclinical hyperthyroidism or hypothyroidism also did not increase the risk for prevalent or incident depression.

Dr. Osvaldo Almeida

"The results of this study add data to an area that has been hitherto guided by 'traditional wisdom.' Like most practitioners, we were trained to believe that subtle thyroid dysfunction could lead to the development of depression[, but] our results show that this is not the case," lead author Osvaldo Almeida, MD, PhD, professor of geriatric psychiatry at the University of Western Australia in Perth, told Medscape Medical News.

"If patients with depression do not show clinical signs suggestive of overt thyroid disease, no useful information is likely to be gained from the systematic screening of thyroid hormones," added Dr. Almeida.

The study is published in the September issue of the American Journal of Geriatric Psychiatry.

Paucity of Data

According to the study, depression affects up to 10% of all adults older than 65 years.

Current practice guidelines recommend testing thyroid function in adults presenting with a depressive episode, "although there is a paucity of data available to support such a recommendation," write the researchers.

"Thyroid function tests have become a routine aspect of the assessment of people with depression[, but] this increases discomfort to patients and costs to both patients and the healthcare system. The problem is that there is no compelling data to support this 'routine' practice," said Dr. Almeida.

The study included 3932 men between the ages of 69 and 87 years (mean age, 75.3 years) who were screened between 1996 and 1999. Follow-up was conducted between 2001 and 2004.

Depressive symptoms were measured using the Geriatric Depression Scale, and depressive episodes were tracked using the Western Australia Data Linkage System. Demographic information and fasting blood samples were collected for all participants, who also underwent thyroid function tests.

Causation 'Unlikely'

Results showed that 4.8% of the men had clinical depression at assessment.

Thyroid-stimulating hormone and free thyroxine levels were similar for those with and without depression, and neither level affected the odds of prevalent depression or the hazard of incident depression.

During the 5-year follow-up period, there was no significant association found between subclinical hypothyroidism and incident depression (hazard ratio, 0.7), and there were no cases of depression found in the men with subclinical hyperthyroidism.

The prevalent depression odds ratio was 0.8 for subclinical hypothyroidism and 1.4 for subclinical hyperthyroidism.

"Taken together, these findings indicate that thyroid hormones are unlikely to play a significant role in the causation of depression in older men," summarize the researchers.

They write that reported links between subclinical thyroid disease and depression from past studies may be a result of selection bias and confounding.

The limitations of the study cited included that it only assessed older men, so its generalizability to women or younger people of either sex is unknown.

Dr. Almeida noted that "a lot of time and money over the past few decades" has been spent looking for a critical factor in the development of depressive symptoms.

"However, it is becoming increasingly clear that depression is not caused by one single factor that, once reversed, would cure depression. Instead, depression arises within a context of personal vulnerabilities and environmental challenges that interact to determine if a person will express the depressive phenotype at a certain point in time," he said.

"I would suggest that the next step is to work out if there is anything we can do to decrease personal vulnerability, determined, for example, by genetic makeup and early life experiences, and minimize the negative physiological consequences of stress. We are currently working to clarify if we can do something about the latter," said Dr. Almeida.

Reconsider Routine Screening

"The authors conclude that routine screening for subclinical thyroid dysfunction among older adults with depression should be reconsidered," write Benjamin Liptzin, MD, and Jimena Tuis, MD, from the Department of Psychiatry at Baystate Medical Center in Springfield, and from Tufts University School of Medicine in Boston, Massachusetts, in an accompanying editorial.

"That could potentially save considerable amounts of money at a time when healthcare costs have been rising around the world and budgets are being squeezed to wring out inefficient or ineffective care," they add.

However, they note that the findings concern screenings in those without a prior history of thyroid dysfunction.

"Individuals with symptoms suggestive of hypo- or hyperthyroidism should have their thyroid function checked and any abnormality followed up. While the article is a reminder that thyroid function is related to mood, energy, concentration, etc. it shows that the yield from routine screening is too low to justify the practice."

The editorialists go on to write that the search for neuroendocrine biomarkers began 30 years ago and has included the possibility of abnormalities in the hypothalamic-pituitary-adrenal axis in those with depression, as shown in dexamethasone suppression tests.

However, enthusiasm for this test waned "as it was recognized that clinical assessments were more helpful in clinical practice." In fact, Dr. Liptzin and Dr. Tuis write that no neuroendocrine testing method has clinical applications for psychiatry at this time.

"Perhaps these tests will attain clinical utility in the future as we better understand the workings and relationships of these psychoneuroendocrine systems."

Overall, they note that this study, and others like it, shows the advances that have been made in understanding the brain and depression.

"Unfortunately, they also highlight the uncertain future as to when or whether these techniques...will lead to improved diagnosis, treatment, or prevention."

The study was supported by grants from the National Health and Medical Research Council of Australia and from the MBF Foundation of Australia. The study authors and editorialists report no relevant financial relationships.

Am J Geriatr Psychiatry. 2011;19:763-770, 759-762. Article abstract, Editorial abstract

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