Category: Thyroid

Monitor: 13

13 - THE ETIOLOGY OF SUPPRESSED TSH IN VETERANS CARED BY A VA MEDICAL CENTER

Thursday, Apr 25
1:30 PM – 2:00 PM

Objective : To analyze the cause of suppressed TSH in randomly selected veteran patients and to improve clinical care/management on the clinical/subclinical hyperthyroidism in the aging veteran population in a VA Medical Center.


Methods :

There were 1294 patients had at least one suppressed TSH value in the year of 2016. 558 patients in alphabetical order were selected. 64 patients were excluded from the study due to insufficient data. 495 patients’ chart were reviewed and analyzed for the cause of low TSH (below 0.55 uU/mL) retrospectively.


Results :

Among the 495 patients studied, 283 (57.2%) were 60 y or older (female=19, 6.9%); 212 were under 60 y (female=52, 24.5%). The most common cause of suppressed TSH was due to thyroid hormone (TH) replacement therapy in the older group (33.2%) with age > 60y; significantly more frequent comparing to the younger group, P<0.001. In patients > 80y (N=50), 25 were on TH, reached 50.0%. Among the 25 patient on T4, 18 had both TSH/FT4 measurements at the same date: mean TSH ( 0.15 uU/mL) and FT4 (1.46 ng/dL, nl 0.67-1.52). Iodine-induced low TSH ranked the 2nd most common cause. CT iodinated contrast and betadine use caused 27.9% in older group as compared to 18.4% in the younger group (P=0.031). The significant difference was due to older veterans received more contrast CTs (P<0.05 as compared to younger group). The suppressed TSH caused by proven diagnosis of hyperthyroidism had similar frequency in both age groups, 5-7%.


Discussion : It is surprising to find that the most common cause inducing suppressed TSH in the aging veteran population is due to TH replacement therapy, especially in age > 80 y. Higher rate in causing below normal TSH following the use of CT with contrast agent is also found in the older age group that is consistent with older veterans receiving more contrast CT studies for cardiovascular(CV) and neoplastic diseases. It is important to recognize that the elderly is at risk to develop iodine-induced thyroid dysfunctions which often are transient and reversible. Thus, the morbidity from excessive therapy can be avoided.  


Conclusion :

In view of the vulnerability to CV/CNS complications and serious consequences in clinical/subclinical hyperthyroidism in the older group, cautious use (and more frequent check on TSH) of TH replacement and CT contrast in aging veterans is recommended.  

Sing yung Wu

Professor
University of California, Irvine and VA Medical Center, Long Beach
Long Beach, California

Professor in Radiological Sciences in UC Irvine and Attending physician at VA Medical Center, Long Beach, California since 1977. He is Johns Hopkins Medical School graduate in 1972.

Mark D. Chambers

Associate Professor
UC Irvine and VA Medical Center, Long Beach

Health Sciences Associate Clinical Professor of Radiology, University of California, Irvine
Section Chief Nuclear Medicine Imaging Service, Radiology/Nuclear Medicine Imaging Service
Veterans Affairs Long Beach Healthcare System

Mazhar Khan

Attending Radiologist
VA Medical Center, Long Beach, California

Attending Radiologist,Radiology/Nuclear Medicine Imaging Service
Veterans Affairs Long Beach Healthcare System
Tibor Rubin Veterans Affairs Medical Center

Constance Chen

Attending Physician
Tibor Rubin Veterans Affairs Medical Center

Board Certified Endocrinologist and attending Physician at Medical Service, Veterans Affairs Long Beach Healthcare System
Tibor Rubin Veterans Affairs Medical Center

Po-yu Yen

Volunteer physician researcher
Research Service, VA Medical Center, Long Beach

Volunteer in the Research/Development Service at Veterans Affairs Long Beach Healthcare System
Tibor Rubin Veterans Affairs Medical Center