A 75-year-old male showed combined anterior pituitary hormone deficiency (CPHD). Basal and TRH-stimulated PRL levels were undetectable. Basal and GRH-stimulated GH levels were very low, and could barely be measured by means of an ultrasensitive enzyme immunoassay. In addition, basal TSH levels were under the normal limit, and TRH-stimulated TSH secretions were impaired. On the other hand, the secretions of ACTH, LH and FSH remained intact. There was no mutation of Pit-1 gene in this patient, and immunohistochemical studies using human pituitary and the patient’s serum showed no positive staining. The HLA types frequently detected in lymphocytic hypophysitis were recognized, supporting the view that the CPHD in this case may be caused by lymphocytic hypophysitis, although magnetic resonance imaging of the pituitary gland showed no specific findings. Interestingly, a high titer of anti-glutamic acid decarboxylase antibody, suggested that the patient suffered from type 1 diabetes mellitus (DM). Five years ago, his thyroid function was normal and the treatment of DM with oral hypoglycemic agent was effective, indicating that the onset of both diseases at least occurred within the last half decade. We report here a rare case of SPIDDM with CPHD which might be caused by lymphocytic hypophysitis.