Suboptimal vitamin D status is commonly observed in primary hyperparathyroidism but is rarely considered in management decisions. The present study aimed to bring additional insights on vitamin D status in primary hyperparathyroidism patients, particularly those presenting with the normocalcemic phenotype. A retrospective study was conducted on 53 confirmed primary hyperparathyroidism patients, stratified into hypercalcemic and normocalcemic groups, hospitalized at the “Pius Brînzeu” Emergency Clinical Country Hospital in Timișoara, Romania. Patients presenting with the normocalcemic phenotype had similar target-organ involvement compared to their counterparts. In this subgroup, 25 hydroxyvitamin D showed an inverse correlation with serum calcium (p = 0.048), and regression analysis identified iPTH and 25OH vitamin D as significant predictors of calcium levels (p < 0.0001; $R^2$ = 0.571). Adenoma volume showed a significant negative correlation with 25OH vitamin D levels (p = 0.021; r = −0.61) but was later found as insignificant after confounder analysis. Postoperative measurements of 25OH vitamin D levels confirmed increasing levels after parathyroidectomy. Our findings highlight a complex relationship between PTH and vitamin D in primary hyperparathyroidism, especially in the often-underdiagnosed normocalcemic phenotype. The inverse correlation between vitamin D and calcium suggests altered homeostasis, rather than true deficiency.

Background: Type I collagen is the most abundant protein of the extracellular matrix. Pathogenic variants in COL1A1 or COL1A2 are classically associated with osteogenesis imperfecta (OI) and Ehlers–Danlos syndrome (EDS). An emerging clinical entity—COL1-related overlap disorder—encompasses individuals exhibiting phenotypic features of both conditions. Methods: We report a 55-year-old male presenting with disproportionate short stature, grayish-blue sclerae, multiple fractures, long bone deformities, joint hypermobility, and atrophic surgical scarring. The patient also had long-standing, untreated childhood-onset hypopituitarism. Imaging studies revealed numerous prior fractures, bowing of forearm bones, and multiple Wormian bones. Results: Genetic testing confirmed a novel heterozygous COL1A1 exon 14 variant (c.940G > A, p.Gly314Arg), presenting with a phenotype consistent with a COL1-related overlap syndrome. Conclusions: This case expands the phenotypic spectrum of COL1A1 mutations and supports the concept of COL1-related phenotypic overlap.

Background: Accurate preoperative localization of hyperfunctioning parathyroid glands remains challenging, particularly in secondary hyperparathyroidism where multiglandular disease may compromise scintigraphic performance. Methods: Our study evaluated biochemical, morphometric, and histopathological predictors of ^99mTc-sestamibi scintigraphy detectability in both primary and secondary hyperparathyroidism. The study group included a total of 162 patients with primary and secondary hyperparathyroidism who underwent dual-phase ^99mTc-sestamibi scintigraphy followed by parathyroidectomy. Demographics, biochemical parameters, histopathological features, lesion volume and scintigraphic findings were assessed at patient and lesion level. Results: In primary hyperparathyroidism, adenomas were larger and more frequently detected than hyperplastic glands. Lesion volume and solid growth pattern were found as positive predictors of sestamibi uptake. In secondary hyperparathyroidism, nodular hyperplasia was associated with larger volume, higher cellularity, and more frequent localizing studies. Upper quadrant position and diffusely hyperplastic lesions were associated with higher lesion miss rates, while lesion volume increased the likelihood of detection. Conclusions: Our findings highlight that ^99mTc-sestamibi scintigraphy performance is strongly influenced by lesion volume, histopathological architecture and anatomical position, underscoring the needs for cautious interpretation of negative or incomplete scans, especially in secondary hyperparathyroidism.