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Low stress hormone levels associated with metabolic disorders in depressed patients

Researchers from Umea University in Sweden have found a correlation between low levels of the stress hormone cortisol and several important modifiable risk factors for type 2 diabetes and cardiovascular disease among patients with affective disorders, such as bipolar disorder and depression.
The study findings, published in the Journal of Affective Disorders, show that low cortisol is often linked to obesity, high levels of fat in the blood and metabolic syndrome in people suffering from recent depression or bipolar disorders.
Bipolar disorder and depression have consistently been associated in the scientific literature with worse biomedical outcomes and increased mortality.
Patients battling with depression have an estimated 10 to15-year reduction in life expectancy, which can be further shortened by contributing factors to metabolic and cardiovascular diseases such as stress, low physical activity and high calorie intake.
Recent studies conducted by researchers from King’s College London have also evidenced that a genetic overlap between type 2 diabetes and depression exists, and that visceral obesity may be one biological explanatory link between type 2 diabetes and depression.
In this study, research scientists hypothesise that a down-regulation of an important stress system in the body called hypothalamic-pituitary-adrenal axis (HPA-axis) could potentially interfere with normal stress response in a depressive illness.
The HPA-axis serves as a crucial feedback loop in the body for interactions among endocrine glands which produce hormones, such as cortisol, that helps regulate the metabolism and control the body’s physiological responses to stress.
The regulation of cortisol release is therefore determined by the activity of the HPA axis.
In healthy individuals, stress normally leads to an overactivity of the HPA-axis, which in turn leads to increased levels of cortisol. If the additional stress is prolonged as it is the case in people with depression and bipolar disorder, however, the stress system is working at a slow pace, with low cortisol levels as a result.
In order to study the link between adrenal insufficiency and metabolic diseases, the research team has measured cortisol levels in 245 patients with bipolar disorder or recurrent depression, together with 258 people in a control group.
Prior to the experiment, patients took a dexamethasone suppression test (DST), used to assess adrenal gland function after injection of dexamethasone, a corticosteroid which enhances cortisol suppression.
The research team, led by Martin Maripuu from the Department of Clinical Sciences, found that participants with bipolar disorder or depression and low levels of cortisol are 34 per cent more susceptible to suffer from obesity, in comparison to 11 per cent among healthy patients.
Dyslipidaemia, i.e high levels of fat in the blood, occurred 42 per cent more often in the affective disorder group compared to 18 per cent in the control group.
And markers of metabolic syndrome were also more prevalent (41 per cent) in patients suffering from depression and bipolar disorder than among their healthy counterparts (26 per cent).
No correlation has however been made between cortisol levels and other specific markers of the metabolic syndromen, like high blood sugar levels or high blood pressure.

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