The goal of this observational study is to create, manage and analyze a multicenter national database of patients affected by hypoparathyroidism or pseudohypoparathyroidism, aimed at collecting and studying anamnestic, diagnostic, genetic, clinical, and therapeutic data in a relatively wide number of patients with these two rare pathologies, in Italy. The study will include 41 specialist clinical centers of endocrinology, pediatric endocrinology, pediatrics, and endocrine surgery, located throughout the Italian territory, and to which patients refer from all the 20 regions of Italy. Data will be collected over time, both in retrospective and prospective manners, during the 10-year duration of the study, starting from the recruiting visit (basal visit) and then during each follow-up visits patients will undergo for the control of disease at the recruiting clinical centers. Collected data will include both the most classic traits of the pathology and the less common ones, with the final goal of refining and deepening medical knowledge in the field of these two clinical conditions affecting parathyroid function and calcium homeostasis, and, thus, to be able to define optimal clinical and therapeutic management of patients, improving their quality of life. The main aspects this observational study aims to assess and clarify are: 1. Evaluation of prevalence and incidence of hypoparathyroidism, globally and in its different etiological forms, and of pseudohypoparathyroidism in Italy. 2. Clinical characterization of different etiological forms of hypoparathyroidism, through both cross-sectional and longitudinal analyses of collected data. 3. Clinical characterization of pseudohypoparathyroidism, through both cross-sectional and longitudinal analyses of collected data. 4. Over time collection of data on bone status and bone fragility in patients with hypoparathyroidism and pseudohypoparathyroidism, to evaluate the prevalence and incidence of fragility fractures in these patients, globally and also based on gender, age, and disease etiology. 5. Over time evaluation of response to pharmacological therapies in patients with hypoparathyroidism and pseudohypoparathyroidism The study will include two independent cohorts of female and male patients of any age, one including patients with chronic hypoparathyroidism of each etiological forms (cohort 1), and one including patients with pseudohypoparathyroidism (cohort 2). The study does not include either any control group/comparison group or healthy volunteers. The study itself does not involve any medical intervention or drug administration. Pharmacological treatments for which data on response to therapy will be collected in the database, are those administered to patients for the control/treatment of hypoparathyroidism or pseudohypoparathyroidism, regardless of their inclusion in this observational study.