first study, DoD hospital-discharge diagnoses by ICD category were determined for 1991, 1992, and 1993, and Gulf War veterans (n = 547,076) were compared with other veterans from the same period (n = 618,335); all were regular active-duty personnel in the Army, Navy (including Marines), and Air Force during the war. All data were obtained from the DMDC. The multivariate ORs for each year were all about 0.9 (exact values not given) adjusted for prewar hospitalizations, sex, age, race or ethnic group, branch of service, marital status, rank, length of service, salary, and occupation; thus deployed Gulf War veterans were not at increased risk for hospitalizations for endocrine, nutrition, or metabolic disorders. In the second study, hospital-discharge records of three hospital systems—DoD (n = 182,164), VA (n = 16,030), and the California Office of Statewide Health Planning and Development (n = 5185)—for 1991-1994 were examined. PMRs of hospital-discharge diagnoses by ICD-9 category were compared for Gulf War veterans and veterans not deployed to the gulf. The PMRs were 0.99 (95% CI 0.93-1.06) for DoD, 1.08 (95% CI 0.92-1.24) for VA, and 0.81 (95% CI 0.48-1.14) for California Office of Statewide Health Planning and Development; all were nonsignificant. All PMRs were adjusted for age and sex, and the DoD PMR was also adjusted for race. Limitations of the studies include the use of hospital-discharge diagnoses and the fact that most endocrine diseases do not require hospitalization.
Several secondary studies assessed thyroid function in Gulf War veterans on the basis of self-reports. A mail survey of the entire Canadian military contingent of 2924 male veterans who served in the Gulf War and 3241 Canadian veterans who were in the military but had not been posted to the gulf region asked about the presence of goiter (a form of thyroid disease) or thyroid trouble. Positive responses were reported by 0.9% of the Gulf War veterans and 0.7% of the nondeployed veterans 20-44 years old and by 2.0% of deployed and 1.3% of nondeployed veterans 45-64 years old; the median age of the deployed was 36 years, and that of the nondeployed was 37 years (Goss Gilroy Inc. 1998).
In the Gray et al. (2002) study discussed above for diabetes, 1.15% of the deployed Seabee veterans reported having a thyroid condition, as did 0.69% of the Seabees deployed elsewhere and 0.97% of the nondeployed Seabees. Comparing thyroid conditions in deployed Seabees and nondeployed Seabees yielded a nonsignificant OR of 1.49 (95% CI 0.89-2.5) adjusted for age, sex, active-duty or reserve status, race or ethnicity, current smoking, and current alcohol-drinking.
As with diabetes, Steele (2000) conducted telephone interviews of 1545 Gulf War-deployed and 435 nondeployed veterans living in Kansas that elicited self-reports of physician-diagnosed or treated thyroid conditions; the condition must have first occurred in 1990-1998. The prevalence of a new thyroid condition was 2% in the deployed group and 1% in the nondeployed group for a nonsignificant OR of 2.32 (95% CI 0.81-6.67) adjusted for sex, age, income, and education level.
Morgan et al. (2000) attempted to determine the effects of military stress on a small group of 72 soldiers undergoing survival training, a realistic simulation of combat. Subjects provided serum samples before the field phase of their training, immediately after a highly intense interrogation phase, and at recovery a day after the end of the experience. During the stress of interrogation, total T3 and free T3 were suppressed. Total and free T4 were slightly increased during interrogation but were decreased at recovery, possibly because of conversion to T3. The authors found an unexplained increase in TSH from baseline to recovery with an