CHICAGO – Higher levels of triiodothyronine (T3) were seen in combatants with PTSD, compared with patients whose PTSD arose from other adverse experiences, according to findings from a systematic review and meta-analysis.
who had experienced childhood or sexual abuse or were a wartime refugee without PTSD (FT3, 0.36 pg/mL higher, and total T3, 31.6 ng/mL higher, respectively; P = .0004 and P less than .00001).
“We found statistically higher free T3 and total T3 levels in patients with [combat-related] PTSD, compared with controls,” said Freddy J.K. Toloza, MD, in an interview during a poster session of the annual meeting of the American Thyroid Association.
However, he noted that there were no overall differences in thyroid-stimulating hormone, free tetraiodothyronine (T4), and total T4 levels between individuals with PTSD and the non-PTSD control participants. In addition, though free and total T3 levels were significantly higher for the overall PTSD cohort than for control participants, the differences were driven by the studies that included combat-exposed individuals.
Dr. Toloza and colleagues included 10 observational studies in their final review and meta-analysis. Five studies looked at war veterans; the others examined individuals who had experienced child abuse or sexual abuse, who were refugees, or who were from the general population.
For inclusion, the studies had to report both mean values and standard deviations for standard thyroid-hormone test values in patients with PTSD, compared with a non-PTSD control group. These included 373 patients with PTSD and 301 control participants. Just under half (47%) were women. None of the studies, wrote the investigators, “compared rates of overt/subclinical thyroid disease between groups.”
There are known links between many endocrine disorders and psychiatric conditions, said Dr. Toloza, but the interplay between disordered thyroid function and neuropsychiatric problems is still being examined. Looking at PTSD is important because it’s estimated that 6%-9% of the U.S. adult population has experienced PTSD over the course of a lifetime.
Levels of thyroid hormones in the systematic review and meta-analysis were still within normal range for the participants with PTSD, acknowledged Dr. Toloza, a research fellow in the division of endocrinology and metabolism at University of Arkansas for Medical Sciences, Little Rock.
However, even though there was no sign of frank thyroid disease in the PTSD population, the elevated T3 levels seen in the analysis are consistent with other studies showing a correlation between higher T3 levels and more-severe PTSD.
It is not known exactly why significant increases in the levels of total and free T3 were seen only in the combat-exposed PTSD population, Dr. Toloza said. “The type of trauma trigger may influence the adaptive responses to stress and might result in diverse thyroid alterations.”
Elevated catecholamine levels, seen in individuals with PTSD, can increase peripheral conversion of T4 to T3, explained Dr. Toloza. Ongoing catecholamine elevation may account for the isolated elevation in T3 levels in the PTSD population. Beta1-adrenergic blockade is an accepted pharmacologic strategy to help alleviate PTSD symptoms.
Dr. Toloza and coinvestigators did not have access to data that would have allowed them to ascertain what types of injuries were sustained by individuals with combat-related PTSD, but he noted in response to a question, that it would be worthwhile to see whether combatants who were blast exposed had different thyroid hormone values than those who were not, because hypothalamic injury is common in blast. This is a future direction Dr. Toloza wishes to pursue.
“Our findings add to the growing literature suggesting that thyroid function changes may be associated with PTSD,” the investigators wrote, but “further research is needed to ascertain the role of thyroid function alterations in PTSD.”
Dr. Toloza reported no financial disclosures or conflicts of interest.