Photo: John Stillwell/PA Wire

Depression and frailty in older age may be linked to thyroid and stress hormone levels, two studies have shown.

One research team found lower morning and higher evening levels of the stress hormone cortisol to be associated with weakness and slower walking speed.

Another discovered that overactive thyroid glands may be a risk factor for depression in the older population.

Both studies appear in the Journal of Clinical Endocrinology & Metabolism, published by the Endocrine Society.

In the first, researchers assessed 745 participants aged 65 to 90. Cortisol levels were measured from saliva samples and tests for physical activity, walking speed, grip strength and weight loss carried out.

An abnormal cortisol pattern marked by higher morning and lower evening levels correlated with criteria for frailty.

“Our results suggest a link between disrupted cortisol regulation and loss of muscle mass and strength,” said research author Hamimatunnisa Johar, from the German Research Centre for Environmental Health in Munich.

The other study involved measuring levels of thyroid-stimulating hormone (TSH) which signals the thyroid gland to become more active.

Researchers analysed TSH data on 1,503 people with an average age of 70.

“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,” said study author Marco Medici, from the Erasmus Medical Centre in Rotterdam, the Netherlands.