Primary hyperparathyroidism is rare in children. A germline mutation is identified in half of all children with primary hyperparathyroidism (70% of newborns and infants, and 40% of children and adolescents). The clinical manifestations of primary hyperparathyroidism in children are highly variable (often absent in newborns, rather severe and symptomatic in children and adolescents) and depend on the genetic cause, as well as the severity, rapidity of onset and duration of hypercalcemia. Morphological investigation and treatment of children and adolescents follow the same rules as for adults. Surgery must be carried out by a surgeon expert in this pathology in children. Primary hyperparathyroidism is rarely diagnosed during pregnancy. Pregnancy-related changes in phosphocalcic homeostasis can sometimes mask its symptomatology, which explains why it is most often asymptomatic and/or undiagnosed due to low levels of hypercalcemia and/or the attribution of certain symptoms (e.g. vomiting) to pregnancy itself. Maternal-fetal morbidity associated with primary hyperparathyroidism during pregnancy, historically considered significant, is in fact rare and depends on maternal calcium levels. Treatment (conservative or surgical) must be adapted to the term of pregnancy, the severity of symptoms and maternal-fetal risks. Primary hyperparathyroidism is common in the elderly. Although the diagnostic approach is comparable to that in younger patients, some clinical specificities of this population need to be considered. In view of the high prevalence of osteoporotic fractures and their consequences for morbidity and mortality in the elderly, surgery is the preferred option in case of osteoporosis. In 2024, the neuropsychological symptoms and cardiovascular impairment associated with primary hyperparathyroidism do not justify parathyroidectomy. Parathyroidectomy is much less frequent than in the younger population, although it remains the first-line treatment, especially as its safety and efficacy have been widely demonstrated.