Sunday, January 20, 2013

Excess Cortisol Increases Fracture Risk

The use of laboratory tests for assessing what may be contributing to bone loss is one of the most important things you and your doctor can do in managing your treatment of osteoporosis. There are numerous lab tests available to physicians that have been found to be correlated in some manner or another with excessive bone loss and/or a heightened risk for breaking a bone.

Cortisol can be one such marker. Cortisol is a hormone produced by the adrenal glands (also called suprarenal glands because they sit atop of the kidneys) in response to stress. Measuring cortisol through saliva is simple, non-invasive, and accurately reflects of the amount of unbound cortisol levels in blood. Because salivary cortisol levels fluctuate throughout the day and night in what is called a circadian, or oscillating, daily rhythm, is most accurately assessed by collecting samples at four specific times throughout a day. If the evening sample is abnormally elevated this is a sign that you are producing too much cortisol and that you may have a condition called subclinical hypercortisolism (SH). What can be difficult about the diagnosis of this condition is that even though a person with SH has an excess production of cortisol, they may not display any of the symptoms common to hypercortisolism (central weight gain, excess sweating, thinning of skin and bruising, high blood pressure, elevated blood glucose, muscle weakness, irritability, etc). Unfortunately, elevated cortisol levels can be asymptomatic, and silently erode away bone density and strength. It is estimated that approximately 1 to 10% of people with osteoporosis have elevated levels of cortisol. In addition, elevated cortisol increases a person's risk for fracture because it not only reduces bone quantity but also the quality of bone. In fact, Morelli et al. (2011) found that in patients with SH who had normal or osteopenic (not osteoporotic!) bone density, 48% sustained fractures compared to 13% in the non-SH group.

In a study conducted by researchers at the University of Milan, Italy, 102 patients with adrenal incidentalomas* (with and without subclinical hypercortisolism) were assessed for bone quality and fracture risk. The authors concluded "that in patients with subtle cortisol excess, TBS (trabecular bone score)[a method of determining bone quality and strength] is reduced and correlates with the number and severity of vertebral fractures and with the degree of cortisol excess."

*Incidentalomas are adrenal gland tumors that have been found incidentally while performing another, unrelated, diagnostic procedure. Approximately 30% of patients with subclinical hypercortisolism are found to have adrenal masses.

Morelli et al. 2011. Risk of new vertebral fractures in patients with adrenal incidenaloma with and without subclinical hypercortisolism: a multicenter longitudinal study. Journal of Bone and Mineral Research. 26:1816-1821. 

Eller-Vainicher et al. 2012. Bone quality, as measured by Trabecular Bone Score (TBS), in patients with adrenal incidentalomas with and without subclinical hypercortisolism. Journal of Bone and Mineral Research. DOI 10.1002/jbmr.1648.




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