A relation between growth hormone (GH) deficiency and immunoglobulin deficiency has been suggested previously in a few cases. We describe a patient with an insulin-like growth factor 1 (IGF-1) deficiency and common variable immune deficiency and briefly review earlier publications on the possible interaction between IGF-1 and the immune system. IGF-1 is the downstream mediator of GH. In this patient, GH and IGF-1 levels were both low. The GH response to a GH-releasing hormone test was normal whereas no subsequent IGF-1 response was seen. In our cohort of 14 patients with hypogammaglobulinaemia, two turned out to have slightly decreased IGF-1 serum levels and one patient with a thymoma had an increased IGF-1 level. Even though IGF-1 may be connected to B lymphocyte differentiation, in this patient we hypothesise there is a common impairment in the IGF-1 and IgG pathways.