More fat around organs in Cushing’s than other cortisol conditions
Fat accumulation associated with diabetes, blood sugar, blood fats
People with Cushing’s disease have more fat in their kidneys and around the heart than those with other conditions with elevated cortisol, a study suggests.
Across all the people evaluated, including those with Cushing’s syndrome, levels of these types of fat were associated with metabolic factors, such as diabetes, blood sugar, and blood fats. While the reasons for the observed relationships must be explored, the researchers believe the findings offer insights for future research.
“To fully understand the effect of … cortisol excess on perivascular and renal sinus fat, prospective studies with a control group of healthy cases are clearly warranted,” wrote the researchers, who said their study might be the first to asses the effect of “endogenous cortisol excess on aortic perivascular [heart] and renal sinus [kidney] fat tissue.”
The study, “Assessment of aortic perivascular and renal sinus fat in endogenous cortisol excess of different etiology,” was published in Hormones.
Cushing’s syndrome is marked by chronically high levels of cortisol in the body. Possible causes include tumors on the adrenal glands that produce the hormone or tumors on the pituitary gland, where it’s known as Cushing’s disease.
Among the many long-term effects of high cortisol is a change in the distribution of fat, which can lead to diabetes, high blood pressure, and cardiovascular disease. High cortisol is particularly thought to lead to ectopic fat accumulation, that is, fats called triglycerides building up in tissues that don’t normally contain much fat.
Fat accumulation in Cushing’s, other conditions
Here, researchers looked at ectopic fat accumulation in people with varying degrees of excess cortisol and its relationship with other coexisting conditions. Specifically, they used MRI to look at aortic perivascular fat, that is, fat surrounding the blood vessels of the heart, and fat in the renal sinus, a compartment of the kidney, in 119 people at a center in Turkey.
Sixteen participants had Cushing’s disease and 21 had adrenal Cushing’s. Another 34 people had mild autonomous cortisol secretion (MACS), where an adrenal tumor gives rise to some elevations in cortisol, but not enough to cause overt symptoms. The remaining 48 people had adrenal tumors, but normal cortisol levels and no clinical symptoms, or nonfunctioning adenomas.
Patients with either type of Cushing’s were younger than the other two groups and generally had higher cortisol than those with MACS. Those with Cushing’s disease had a higher body mass index (BMI), an indicator of body fat, than the other groups. They also tended to have more metabolic risk factors, including higher triglycerides and blood sugar.
Aortic perivascular fat levels were significantly higher in those with Cushing’s disease than those with adrenal Cushing’s or nonfunctioning adenomas.
Statistical analyses adjusted for age, sex, and BMI showed Cushing’s disease patients still had significantly higher aortic perivascular fat levels than those with MACS or nonfunctioning adenomas. Those with Cushing’s disease also had significantly higher renal sinus fat relative to those with MACS.
Researchers said they couldn’t explain these increases in ectopic fat with Cushing’s disease relative to other causes of high cortisol, but suspect it might have to do with a longer exposure to high cortisol. Such data were not available to be analyzed, however. The relatively higher rates of metabolic risk factors could play a role.
Indeed, across the entire study group, the amount of renal sinus fat was significantly higher in patients with diabetes than those without it and positively correlated with blood sugar levels. Moreover, the amount of perivascular fat positively correlated with triglyceride levels and body weight.
In final analyses, researchers determined that high cortisol after a dexamethasone suppression test, which is used to diagnose Cushing’s, and high triglycerides were associated with more perivascular fat, whereas being female was associated with lower levels.
More research is “needed to elucidate the mechanism of action underlying perivascular and renal sinus fat distribution,” especially since this could mean added cardiovascular risks, wrote the scientists, who noted their study was limited by the lack of a proper control group. While people with nonfunctioning adenomas have normal cortisol levels, they’re not metabolically normal relative to the general population, so a healthy control group must be included.
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