Persistent hypercalcaemia associated with two pathogenic variants in the CYP24A1 gene and a parathyroid adenoma-a case report and review.

Introduction: 24-Hydroxylase, encoded by the CYP24A1 gene, is a crucial enzyme involved in the catabolism of vitamin D. Loss-of-function mutations in CYP24A1 result in PTH-independent hypercalcaemia with high levels of 1,25(OH)2D3. The variety of clinical manifestations depends on age, and underlying genetic predisposition mutations can lead to fatal infantile hypercalcaemia among neonates, whereas adult symptoms are usually mild. Aim of the study: We report a rare case of an adult with primary hyperparathyroidism and loss-of-function mutations in the CYP24A1 gene and a review of similar cases. Case presentation: We report the case of a 58-year-old woman diagnosed initially with primary hyperparathyroidism. Preoperatively, the suspected mass adjoining the upper pole of the left lobe of the thyroid gland was found via ultrasonography and confirmed by 99mTc scintigraphy and biopsy as the parathyroid gland. The patient underwent parathyroidectomy (a histopathology report revealed parathyroid adenoma), which led to normocalcaemia. After 10 months, vitamin D supplementation was introduced due to deficiency, and the calcium level remained within the reference range. Two years later, biochemical tests showed recurrence of hypercalcaemia with suppressed parathyroid hormone levels and elevated 1,25(OH)2D3 concentrations. Further investigation excluded the most common causes of PTH-independent hypercalcaemia, such as granulomatous disease, malignancy, and vitamin D intoxication. Subsequently, vitamin D metabolites were measured using LC-MS/MS, which revealed high levels of 25(OH)D3, low levels of 24,25(OH)2D3 and elevated 25(OH)2D3/24,25(OH)2D3 ratios, suggesting a defect in vitamin D catabolism. Molecular analysis of the CYP24A1 gene using the NGS technique revealed two pathogenic variants: p.(Arg396Trp) and p.(Glu143del) (rs114368325 and rs777676129, respectively). Conclusions: The diagnostic process for hypercalcaemia becomes complicated when multiple causes of hypercalcaemia coexist. The measurement of vitamin D metabolites using LC-MS/MS may help to identify carriers of CYP24A1 mutations. Subsequent molecular testing may contribute to establishing the exact frequency of pathogenic variants of the CYP24A1 gene and introducing personalized treatment.

Musculoskeletal complications of Cushing syndrome.

Prolonged exposure to an excess of glucocorticosteroids (GCs), both endogenous and exogenous, leads to a wide range of comorbidities, including cardiovascular, metabolic, psychiatric, and musculoskeletal disorders. The latter comprise osteopenia and osteoporosis leading to skeletal fractures and myopathy. Although endogenous hypercortisolemia is a rare disorder, GCs are among the most frequently prescribed drugs, often administered chronically and despite multiple side effects, impossible to taper off due to therapeutic reasons. The pathophysiology of the effect of GC excess on bone often leads to fractures despite normal or low-normal bone mineral density and it includes direct (mainly disturbance in bone formation processes, through inactivation of the Wnt/ß-catenin signalling pathway) and indirect mechanisms (through suppressing the gonadal and somatotrophic axis, and also through antagonizing vitamin D actions). Glucocorticosteroid-induced fast-twitch, glycolytic muscles atrophy occurs due to increased protein catabolism and impaired synthesis. Protein degradation is a result of activation of the ubiquitin proteasome and the lysosomes stimulated through overexpression of several atrogenes (such as FOXO-1 and atrogin-1). This review will discuss pathophysiology, clinical presentation, prevention, and management of GC-induced osteoporosis (including calcium and vitamin D supplementation, and bisphosphonates) and myopathy associated with GC excess.

The Effect of a Single High Dose of Vitamin D on Serum Levels of Its Metabolites in the Elderly.

BACKGROUND: Vitamin D is a dietary micronutrient responsible for calcium and phosphorus metabolism and multiple extraskeletal actions. The assessment of vitamin D status is commonly based on measurement of 25(OH)D total concentration in serum. However, the usage of liquid chromatography with tandem mass spectrometry (LC-MS/MS) technique allows to reliably assess a panel of vitamin D metabolites in serum or plasma, which may help to investigate the metabolic paths of vitamin D, especially in populations at risk of deficiency. METHODS: A randomized, two-arms, open study was conducted on 58 patients (28 female and 30 male; aged from 61 to 96 years old). The primary aim was to assess the effects of a single, high, oral dose of vitamin D3 (120,000 IU) on serum 25(OH)D3, 25(OH)D2, 24,25(OH)2D3, 3-epi-25(OH)D3, 1,25(OH)2D3, 24,25(OH)2D3/25(OH)D3 ratio, and 25(OH)D3/3-epi-25(OH)D3 ratio concentration (measured by LC-MS/MS) at baseline, 3 days and 7 days after administration, compared to control group. The secondary aim was assessment of influence of percentage of fat tissue on serum metabolites of vitamin D and their changes after bolus dose. RESULTS: 56.6% study group attained a serum 25(OH)D3 concentration >30 ng/mL. All subjects, except for one patient achieved a serum 25(OH)D3 concentration >20 ng/mL after administration. No one exceed reference value of vitamin D (30-50 ng/mL). Among participants who received vitamin D3 there were significant increase in 25(OH)D3, 3-epi-25(OH)D3, 1,25(OH)2D3, 24,25(OH)2D3 on 3rd day after administration. 24,25(OH)2D3 concentration gradually grew, achieving the highest concentration on 7th day. The percentage increase of 25(OH)D3 was negatively correlated with baseline 25(OH)D3 (r = -0.688, p = 0.001). Positive correlation between percentage increase in 25(OH)D3 and a percentage increase serum concentration of 24,25(OH)2D3 (r = 0.954, p < 0.001), 3-epi-25(OH)D3 (r = 8.03, p < 0.001) and 1,25(OH)2D3 (r = 0.789, p <0.001) were found. None of the study participants developed hypercalcemia. The baseline concentration of analyzed metabolites of vitamin D in serum and their percentage increase were neither dependent on BMI nor percentage of fat tissue. CONCLUSIONS: High dose of vitamin D rapidly increases 25(OH)D3 concentration in the elderly patients. The response to the bolus of vitamin D includes activation of 3-epimerase, followed by production of 24,25(OH)2D3, which protects from excessive increase of active form of vitamin D.

The effect of biotin interference on the results of blood hormone assays.

Approximately 70% of medical decisions are made based on results of laboratory investigations. Immunochemical methods are used most commonly in routine laboratory diagnostics of endocrine disorders. Those methods are limited by susceptibility of the immunochemical reaction to various interferences. Interference may be caused by the presence of autologous antibodies, heterophilic antibodies, or paraproteins in the blood serum, by cross-reactions with similar reagents, haemolysis, significant lipidaemia, or hyperbilirubinaemia. Some recent reports have indicated a significant effect of biotin on the reliability of laboratory investigations. Biotin is a water-soluble vitamin belonging to the B group. It is present in popular dietary supplements - alone or as a component of multi-vitamin formulas - and it is advertised as a remedy to falling out and fragility of hair and nails. Due to its low molecular weight and a strong affinity to streptavidin, biotin is used in many immunochemical tests. Due to a strong and stable bond of streptavidin and biotin, analytical methods using the streptavidin (avidin)-biotin system are characterised by superior sensitivity, and they allow determination of very low levels of the tested substance in biological material. The presence of exogenous biotin in a sample may cause interference when using tests that utilise the streptavidin (avidin)-biotin system. Interference of biotin with immunochemical tests depends on several factors: the construction of the immunochemical test, the dose used by the patient, the biotin concentration in the sample, and most of all - the time from the last dose to the collection of biological material for laboratory testing. In this paper we present some practical recommendations and a procedure to be followed in the case of suspected interference of biotin in immunochemical assays, for clinicians and laboratory diagnosticians.