Thyrotropic involvement is considered to be constant in Sheehan's syndrome. In this study, plasma thyroid stimulating hormone (TSH) levels were similar to those of normal women (respectively: 1.01 +/- 0.54 ng/ml and 0.54 +/- 0.27 ng/ml). The pituitary response to the administration of TRH was nul in 63.8% of cases. In one patient, thyrotrophic function was normal. Twelve patients had a minimal or moderate reserve of TRH. By order of prevalence, thyrotrophic involvement succeeds that of the somatotrophic and lactotrophic axes. There is no correlation with involvement of other axes which would make it possible to define a sequential course of pituitary lesions. These results are discussed in the light of the existing literature. The TRH test does not offer certain evidence of hypothalamic involvement.