Medication Adherence and Its Impact on Biochemical Outcomes and Quality of Life in Hypoparathyroidism and Related Endocrine–Metabolic Disorders: A Systematic Review and Meta-Analysis

Objectives: This study aimed to evaluate adherence to therapy in hypoparathyroidism and related endocrine–metabolic disorders and to assess its association with biochemical outcomes, hypocalcemia episodes, and health-related quality of life (HRQoL). Methods: In accordance with PRISMA 2020 guidelines, PubMed, Scopus, Google Scholar, and the Cochrane Library were searched until September 2025. The eligible studies were randomized controlled trials, cohort, case–control studies, cross-sectional, and observational studies that reported adherence to calcium/vitamin D or recombinant parathyroid hormone therapy. Results: twenty-three studies were included in the qualitative synthesis, and 11 studies were included in the quantitative meta-analysis. Pooled medication adherence compliance was 70–82% and improved with simplified regimens and the use of recombinant PTH. Additionally, this was also associated with an improvement in HRQoL (p < 0.0001) and a lower risk of hypocalcemia (p < 0.0001). Conversely, multifactorial regulation was observed as the level of adherence had no significant effect on serum calcium levels (p = 0.7116). Sensitivity analyses demonstrate the strength of findings and indicate no significant publication bias. Conclusions: Medication adherence is a key factor in determining patient-centered outcomes in hypoparathyroidism. Better adherence is linked to a higher quality of life and fewer episodes of hypocalcemia, while its effect on biochemical parameters seems minimal. Educational programs, simple treatment regimens, and wider access to rhPTH therapy can be used to improve patient management of the disease over time.