An Open-label Phase 4 Study to Explore Immunogenicity of the Liquid Formulation of Saizen® in Subjects With Adult Growth Hormone Deficiency (AGHD)

Inclusion Criteria: * Male and female subjects, 18-65 years of age, inclusive, at the time of signature of informed consent * Documented AGHD i.e. childhood onset (CO) or adult onset (AO), either by a stimulation test as described in the GH Research Society's 2007 guidelines for the diagnosis and treatment of AGHD, or in the Saizen® label, whichever is more stringent, or by confirming the presence of at least 3 pituitary hormone deficiencies and an IGF-1 level below the reference range of the laboratory where testing is performed. Stimulation test as described in the 2007 GH Research Society guidelines and applicable to all subjects who underwent or will undergo a stimulation test: * Insulin Tolerance Test (ITT) or glucagon stimulation test: Peak GH less than 3 nanogram per milliliter (ng/mL); * GH-releasing hormone (GHRH) plus arginine test, peak GH depends on body mass index (BMI): * BMI less than 25 kilogram per square meter (kg/m\^2) indicates a peak GH less than 11 ng/mL microgram per liter \[mcg/L\]). * BMI 25-30 kg/m\^2 indicates a peak GH less than 8 ng/mL (mcgg/L). * BMI greater than 30 kg/m\^2 indicates a peak GH less than 4 ng/mL (mcg/L). Clonidine, l-dopa, and arginine alone are not acceptable as stimulation tests for determining eligibility in this trial. Stimulation tests remain under the Investigator's or the subject's physician's responsibility, including the selection of the GH assay. Saizen® label: in Europe, only one single test is requi…