We present a case of a 60-year-old male patient with diagnosis of non-Hodgkin’s lymphoma (NHL): diffuse large B cell lymphoma (non-Hodgkin’s DLBCL), who achieved complete remission after first-line treatment. Eleven months later he was admitted to our hospital again with symptoms of the disease’s systemic relapse and central nervous system (CNS) infiltration. He developed new and serious symptoms of complete pituitary gland insufficiency. Magnetic resonance imaging findings and hormone serum levels confirmed the CNS infiltration and insufficiencies of the pituitary as well as its dependent peripheral glands. Chemotherapy and hormonal substitution significantly improved the patient’s condition for several months. That is why, in the case of deteriorated patient condition, we have to consider possible secondary development of pathological processes in the course of the primary disease.