The results of the thyrotropin-releasing hormone (TRH) stimulation test and the combined dexamethasone/corticotropin-releasing hormone (DEX/CRH) test are believed to correlate with social support status in patients with major depressive disorder. We studied 41 consecutive patients hospitalized for major depressive disorder and tested their responses to DEX/CRH and TRH on hospital days 4-7. DeltaMAX TSH and DeltaMAX cortisol were measured. Multiple regression analysis found that social support questionnaire (SSQ-A) and SSQ-B scores were significantly related to DeltaMAX cortisol and DeltaMAX TSH, respectively, at the time of admission. Social support might contribute partially to the TRH and DEX/CRH test results in patients with major depressive disorder.