Hypomagnesaemia leading to parathyroid dysfunction, hypocalcaemia, and hypokalaemia as a complication of long-term treatment with a proton pump inhibitor - a literature review.

Proton pump inhibitors (PPIs) are one of the most frequently used medications worldwide. The side effects of this class of drugs have been widely studied. However, their impact on the electrolyte balance is frequently forgotten. Long-term PPI administration can lead to profound electrolyte disturbances, namely hypomagnesaemia as well as, secondary to very low magnesium levels, hypocalcaemia and hypokalaemia. In this paper we comprehensively review the complexity of the mechanisms contributing to electrolyte imbalance following PPI (proton pump inhibitors) by changing the pH in the intestinal lumen, interfering with the active cellular transport of magnesium regulated by the transient receptor potential melastatin cation channels TRPM6 and TRPM7. The accompanying hypomagnesaemia causes unblocking of the renal outer medullary potassium channel (ROMK), which results in increased potassium loss in the ascending limb of the loop of Henle. Hypokalaemia caused by hypomagnesaemia is resistant to potassium supplementation because the loss of this element in urine increases with the supply of potassium. Additionally, within the calcium-sensitive receptor (CASR), dissociation of magnesium from the alpha subunit of G protein caused by hypomagnesaemia increases its activity, leading to inhibition of PTH secretion and hypocalcaemia resistant to calcium supplementation. All this means that in some patients, chronic use of proton pump inhibitors by affecting the absorption of magnesium, may lead to life-threatening electrolyte disorders.

[68Ga]Ga-DOTA-TATE in diagnosis of MEN syndrome.

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Do large parathyroid adenomas increase the risk of severe hypercalcemia?

<b><br>Introduction:</b> Primary hyperparathyroidism (PHPT) is mainly caused by parathyroid adenoma (PA). Rare variants of PA, weighing >2.0-3.5 g are called "large" or "giant" adenomas and account for about 1.5% of all PA.</br> <b><br>Aim:</b> The aim of this study was to compare normal-sized and large parathyroid lesions identifying risk factors for severe hypercalcemia.</br> <b><br>Materials and methods:</b> 27 patients with PHPT and parathyroid lesion ≥2.0 cm3 (study group) were compared with 73 patients with PHPT and lesion < 2.0 cm³ (control group). In both groups, the majority were women (81.5% - study group, 90.5% - control group, gender ratios 4.4:9.1, respectively). The patients were examined preoperatively and postoperatively: PTH, creatine, calcium, and phosphate serum and urine concentrations, and calcidiol serum levels were assessed. Preoperative ultrasonography (US) was performed.</br> <b><br>Results:</b> Patients with larger parathyroid lesions had signifficantly higher PTH and calcium serum concentrations and lower serum phosphate and calcidiol concentrations. There were no statistically significant differences in the concentration of creatine in serum and urine, calciuria, or tubular reabsorption of phosphorus (TRP). US relatively underestimated the parathyroid volume by about 0.3-0.4 mL (10% in larger lesions and 43% in smaller ones).</br> <b><br>Conclusions:</b> Due to higher PTH and calcium levels, larger parathyroid adenomas may constitute a higher risk of severe hypercalcemia. In general, US underestimated the parathyroid volume.</br>.

Cystic Parathyroid Adenomas as a Risk Factor for Severe Hypercalcemia.

(1) Background: Parathyroid cystic adenomas (PCA) are rare entities representing only 0.5-1% of parathyroid adenomas, accounting for 1-2% of cases of primary hyperparathyroidism (PHPT). The purpose of this study was to compare classical and functional/secreting cystic parathyroid lesions and identify risk factors for severe hypercalcemia; (2) Methods: A total of 17 patients with PHPT and parathyroid cysts (study group) were compared with the group of 100 patients with hyperparathyroidism caused by adenoma or hyperplasia (control group). In both groups the majority were women (88% vs. 12%, with gender ratio 7, 3:1). The patients were examined preoperatively and postoperatively: PTH, creatine, calcium and phosphate serum and urine concentrations and calcidiol serum levels were assessed; (3) Results: Patients with parathyroid cyst had statistically higher PTH and calcium serum concentration, higher calciuria and lower serum phosphate concentration. There were no statistically significant differences in the concentration of creatine in serum and urine and tubular reabsorption of phosphorus (TRP); (4) Conclusions: Due to higher PTH and calcium levels, cystic parathyroid adenomas could be one of the rare risk factors for severe hypercalcemia and hypercalcemic crisis which can be life threatening.

Association Between Parafibromin Expression and Presence of Brown Tumors and Jaw Tumors in Patients with Primary Hyperparathyroidism: Series of Cases with Review of the Literature.

BACKGROUND Brown and jaw tumors are rare entities of poorly understood etiology that are regarded as end-stage of bone remodeling in patients with long-lasting and chronic hyperparathyroidism. Jaw tumors are mainly diagnosed in jaw tumors syndrome (HPT-JT syndrome) and are caused by mutation in the CDC73 gene, encoding parafibromin, a tumor suppressing protein. The aim of this work is to present 4 cases of patients in whom the genetic mutation of the CDC73 gene and clinical presentation coexist in an unusual setting that has not yet been described. CASE REPORT We present cases of 4 patients with primary hyperparathyroidism. Three were diagnosed with brown tumors (located in long bones, ribs, iliac, shoulders) and 1 with brown and jaw tumors. Expression of parafibromin in affected parathyroid tissues were analyzed. In patients without positive parafibromin staining, we searched for CDC73 mutation using next-generation sequencing. Parafibromin staining was positive in 1 patient with brown tumors and was negative in 2 individuals with brown tumors and 1 with brown and jaw tumors. CDC73 mutation was detected in two-thirds of patients (60%) with negative staining for parafibromin and brown tumors. MEN1 mutation was found in the patient with brown tumor and positive staining for parafibromin. CONCLUSIONS Patients with hyperparathyroidism and coexistence of brown tumors or jaw tumors might have decreased expression of parafibromin in parathyroid adenoma tissue, which might be caused by CDC73 mutation and suggest a genetic predisposition. Further research on much larger study groups is needed.

A Woman with a 27-Year History of Hyperparathyroidism and Hypercalcemia Who Was Diagnosed with Low-Grade Parathyroid Carcinoma.

BACKGROUND Parathyroid carcinoma (PC), accounting for 0.005% of all cancers, is responsible for less than 1% of all cases of primary hyperparathyroidism, and equally affects males and females, usually in 4th or 5th decades of life. PC can occur sporadically and can be associated with congenital genetic syndromes such as hyperparathyroidism-jaw tumor syndrome (HPT-JT), isolated familial hyperparathyroidism, or multiple endocrine neoplasia 1 and 2 syndromes. Surgery is the main treatment, with a limited role of radio- and chemotherapy, which allows 49-77% of patients to survive 10 years. In this work we report the case of a patient with parathyroid carcinoma, whose treatment required 13 surgeries over a period of 27 years, together with radiotherapy and pharmacological treatment. CASE REPORT A 51-year-old woman was first diagnosed with primary hyperparathyroidism in 1993 at the age of 23. From 1993 to present, she underwent 13 surgeries and 33 courses of radiotherapy due to recurrent lesions, which initially had a character of parathyroid adenomas, then parathyromatosis, and finally were diagnosed as parathyroid carcinoma. The patient also required and currently requires complex pharmacological treatment to control the calcemia and manage the complications of the primary disease. Supervision by the multidisciplinary professional medical team allows the patient to lead a normal life with good control of the disease. CONCLUSIONS Parathyroid carcinoma is a rare disease with a number of complications; however, obtaining satisfactory long-term survival with acceptable quality of life is achievable.

Treatment of pathological fractures due to brown tumours in a patient with hyperparathyroidism and lack of parafibromin expression - A case report.

Brown tumours, known also as osteitis fibrosa cystica, are benign osteolytic lesions found in 5-15% of patients with hyperparathyroidism, and commonly located in mandibles, the shafts of long bones, the pelvis or ribs. As they compromise bone strength, pathological fractures can be a typical effect of their presence; but given the complex nature of the disease process in this case, such fractures require an interdisciplinary approach directed at orthopaedic treatment, plus management of the underlying hyperparathyroidism. In this paper, we present the case of a 36-year-old female patient with bilateral anophthalmia, hyperparathyroidism and nephrolithiasis, in whom a fall led to her sustaining a pathological fracture of the proximal third of the femoral shaft in the place of an osteolytic lesion, as well as second pathological fracture of the left patella also changed by multiple examples of such lesions. Parathyroidectomy on account of adenoma had been performed 2 weeks prior to the trauma. The femoral shaft fracture was treated surgically, the patella fracture conservatively, and a sample brown tumour was found in tissue. As the parathyroid showed no parafibromin expression, a diagnosis of HPT-JT (hyperparathyroidism and jaw tumour) was arrived at, with this condition given as caused by CDC73 mutation. This disease is able to account for brown tumours, hyperparathyroidism, benign or malignant tumours of kidneys, intestinal tract, and lungs. The approach combining treatment of the fractures with intervention over the parathyroid adenoma proved a successful one, with complete bone union ensuing, and no relapse into hyperparathyroidism 2 years on from the surgery. This case indicates the importance of an interdisciplinary approach to the treatment of brown tumours, as well as the necessity for a diagnosis to be extended when incidental brown tumours are found.

A Novel Germline c.1267T>A MEN1 Mutation in MEN1 Family-from Phenotype to Gene and Back.

Primary hyperparathyroidism is a relatively common endocrine disorder, which may be hereditary. This report describes clinical, biochemical, radiographic, and genetic findings, the latter obtained using next generation sequencing (NGS), in three consanguineous patients. Gene panels in NGS consisted of 5 or 70 genes, including MEN1 and RET. The first patient suffered from recurrent primary hyperparathyroidism. Primary hyperparathyroidism and pituitary microadenomas were afterwards diagnosed in two of her daughters. No clinical nor radiological features of gastroenteropancreatic neuroendocrine tumors were found. All three family members were heterozygous for MEN1 NM_130799: c.1267T>A transversion, which is predicted to result in substitution of tryptophan with arginine in position 423. Additionally, the first patient was also a carrier of RET NM_020975: c.1946C>T missense mutation, which was not present in two other family members. We describe a family with a novel heterozygous mutation (NM_130799: c.1267T>A) in MEN1 gene and postulate that it leads to MEN1 syndrome. The study underlies the importance of genetic testing in primary hyperparathyroidism in personalizing patients' care.

Life-threatening hypophosphataemia secondary to zoledronic acid implementation in a middle-age patient who presented with advanced osteolysis in the course of multiple myeloma.

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High dose intravenous methylprednisolone pulse therapy causes transient increase of serum calcium and phosphate levels.

High and very high doses of intravenous methylprednisolone (IVMP) administered in pulses are the first-line treatment for active, moderateto- severe, as well as sight-threatening Graves' orbitopathy (GO). However, glucocorticoid therapy is associated with side effects, among others, it affects bone metabolism. AIM: The aim of study was to assess the acute effects of high and very high doses of IVMP on calcium (Ca) and phosphate (P) balance in euthyroid patients with moderate-to-severe GO and sight-threatening GO due to dysthyroid optic neuropathy (DON). MATERIALS AND METHODS: Thirty-six patients with active, moderate-tosevere GO were treated with twelve once-weekly pulses (with cumulative dose of 4.5 g IVMP) and 11 patients with DON received 3 intravenous pulses of 1.0 g IVMP on three consecutive days. We measured serum levels of Ca and P at baseline and on the following days after the beginning of the IVMP therapy. RESULTS: We observed a significant increase in serum Ca level on the next day after the 1st IVMP pulse both in patients with moderate-tosevere GO and with DON. Then, on the day 3, the decrease of serum Ca was noticed. In patients with moderate-to-severe GO, on the day 2 serum P showed a significant increase and then, it returned to basal level on the day 3. CONCLUSIONS: We observed a significant increase in serum Ca level on the next day after the 1st IVMP pulse both in patients with moderate-tosevere GO and with DON. Then, on the day 3, the decrease of serum Ca was noticed. In patients with moderate-to-severe GO, on the day 2 serum P showed a significant increase and then, it returned to basal level on the day 3.

Therapy of moderate-to-severe Graves' orbitopathy with intravenous methylprednisolone pulses is not associated with loss of bone mineral density.

PURPOSE: To evaluate the influence of intravenous methylprednisolone (IVMP) pulse administration on bone mineral density (BMD) of the lumbar spine and the femoral neck in patients with moderate-to-severe Graves' orbitopathy (GO). METHODS: Thirty-five patients with GO in euthyreosis were treated with 12 IVMP pulses (6 × 0.5 g, 6 × 0.25 g on a weekly schedule). Supplementation with 1.0 g of calcium and 800 IU of vitamin D was initiated in all patients before beginning therapy. BMD of the lumbar spine (L1-L4) and the femoral neck were assessed at baseline and after the last IVMP pulse using dual-energy X-ray absorptiometry. To determine differences in BMD between values at baseline and after treatment, we used the least significant change (LSC) methodology. LSC values were calculated to be 3 and 5% for the lumbar spine and the femoral neck, respectively. Change in BMD equal to or exceeding the LSC was assessed as either increase or decrease of BMD. We then compared pre-treatment and post-treatment mean BMD values at the lumbar spine and the femoral neck. RESULTS: We did not observe a decrease of BMD at any site equal to or exceeding the LSC. We found an increase of BMD in at least one measurement site equal to or exceeding the LSC value in 43% of patients, mostly in the lumbar spine (31%). Mean femoral neck BMD did not change while mean lumbar BMD increased. CONCLUSIONS: IVMP given in weekly intravenous pulses does not lead to loss of BMD of the lumbar spine and the femoral neck.

Milk-alkali syndrome (MAS) as a complication of the treatment of hypoparathyroidism - a case study.

Milk-alkali syndrome (MAS), characterized by renal failure, metabolic alkalosis and hypercalcemia, is a severe and life-threatening complication of the treatment of hypoparathyroidism. The clinical course is often sudden and is not preceded by any prodromal symptoms. Occurrence does not depend on the duration of hypoparathyroidism treatment, although it is closely related to the applied therapy, especially the dose of calcium carbonate and active vitamin D preparations. Drugs influencing the glomerular filtration rate (angiotensin receptor blockers, sartans, aldosterone receptor antagonists, thiazide diuretics), lack of adequate routine control, changing the calcium carbonate supplementation, dehydration, a diet rich in pH-basic foods (i.e. vegetarian diet), pregnancy and other associated conditions are listed among the factors triggering MAS. A higher calcium carbonate dose is directly associated with an increased risk of milk-alkali syndrome. In case of a high calcium demand it is necessary to control renal function and monitor the level of calcium in the serum more frequently, aiming for the lower end of the reference range. If MAS has been confirmed or if there are alarming neurological symptoms suggestive of hypercalcemia, the patient must be sent to the hospital immediately. Treatment of MAS involves: discontinuation of calcium and vitamin D supplementation, and intravenous infusion of normal saline solution to eliminate volume deficiencies and to achieve forced diuresis while maintaining proper fluid balance. As soon as there is improvement in the patient's clinical condition, it is necessary to begin the treatment of comorbidities increasing the risk of renal failure or alkalosis (i.e. vomiting, diarrhea).

Treatment of severe life threatening hypocalcemia with recombinant human teriparatide in patients with postoperative hypoparathyroidism - a case series.

INTRODUCTION: Hypocalcaemia is a common postoperative complication, both after the resection of parathyroid adenoma associated with primary hyperparathyroidism and after total thyroidectomy due to thyroid cancer or nodular goitre. For a few years, in patients with postoperative hypoparathyroidism and severe hypocalcaemia, who cannot discontinue intravenous calcium preparations even with the use of high vitamin D doses, attempts have been made to add recombinant human parathormone (rhPTH) to the treatment schedule. In this work, for the first time in Poland, we demonstrate the potential use of teriparatide for the treatment of severe hypocalcaemia based on three different cases of postoperative hypoparathyroidism. MATERIAL AND METHODS: Case 1. Female (52) with postoperative hypoparathyroidism, after total thyroidectomy and the removal of lower left parathyroid gland due to hyperparathyroidism, several weeks after the surgery still required intravenous calcium infusions because of tetany symptoms. Just one month of teriparatide treatment at 20 µg/0.08 mL given in daily subcutaneous injections proved sufficient to control calcium levels with oral calcium and vitamin D preparations during the next few days until total resolution of hypocalcaemia symptoms and the achievement and maintenance of laboratory normocalcaemia in the following weeks. CASE 2: Female (33) with hypoparathyroidism following total thyroidectomy in 1996 because of papillary thyroid cancer, with congenital tubulopathy associated with renal loss of calcium and magnesium, and the symptoms of tetany recurring since the day of surgery, requiring intravenous calcium administration every 2-3 days. Currently, the patient has been hospitalised because of venous port infection, the only venous access, which made intravenous therapy impossible. Because of the life-threatening condition of the patient, bridging teriparatide treatment was prepared (20 µg/0.08 mL). Complete resolution of clinical symptoms of hypocalcaemia was obtained with teriparatide doses given every 8-12 hours, which made dose reduction possible. Case 3. Female (52) after major oncological surgery because of laryngopharyngeal and cervical oesophageal cancer with the removal of parathyroid glands, fed through PEG, was admitted to hospital with the symptoms of tetany. Despite treatment intensification, the patient experienced a hypocalcaemic crisis during hospitalisation. Teriparatide treatment at 2 × 20 µg/day resulted in the resolution of tetany symptoms, with gradual normalisation of calcium-phosphate balance parameters during the following days. CONCLUSIONS: Based on the analysis of these cases, the conclusion was drawn that the use of recombinant human teriparatide allows for the control of severe hypocalcaemia requiring intravenous infusions of calcium in patients with postoperative hypoparathyroidism. (Endokrynol Pol 2016; 67 (4): 403-412).

[Life-threatening hypophosphatemia in 74-year-old woman with recurrent pneumonia and progressive muscular atrophy]. / Zagrazajaca zyciu hipofosfatemia u 74-letniej kobiety z nawracajacym zapaleniem pluc i postepujaca atrofia miesni.

UNLABELLED: Although hypophosphatemia can be a serious threat to health and life, it is a problem rarely taken into consideration in the differential diagnosis in the current clinical practice. The aim of the study was to present the description of hypophosphatemia issues in the context of the threat they may pose to the health and life when undiagnosed. CASE REPORT: 74-year-old internal charged woman , with progressive destruction for a few years, recurrent pneumonia, and a compression fracture of the spine, was admitted to hospital because of fainting and general deterioration. In the course of the performed diagnostics primary hyperparathyroidism was diagnosed with pre-existing inadequate severe hypophosphatemia. Because the presented clinical picture, only partially tie in symptomatology of primary hiperparathyroidism, the diagnostic process was targeted to search for other causes of both hypophosphatemia and symptoms reported by the patient. Finally, in addition to PHPT ( primary hyperparathyroidism) also vitamin D deficiency and tuberculosis was found. The fact that the treatment of infectious disease led to the phosphatemia standardization , and thus to significant improvement of the overall demonstrates, shows the significant contribution of tuberculosis in the pathogenesis of phosphate deficiency in this case. RESULTS: Our case is an example of confirming the need for a thorough and multidirectional analysis of the clinical picture, which is a prerequisite for a correct diagnosis.

Unilateral laparoscopic adrenalectomy following partial transsphenoidal adenomectomy of pituitary macroadenoma - life-saving procedure in a patient with ACTH-dependent Cushing's syndrome.

INTRODUCTION: Cushing's disease is the most common cause of endogenous hypercortisolemia, in 90% of cases due to microadenoma. Macroadenoma can lead to atypical hormonal test results and complete removal of the tumour is unlikely. CASE REPORT: A 77-year-old woman with diabetes and hypertension was admitted because of fatigue, proximal muscles weakness, lower extremities oedema, and worsening of glycaemic and hypertension control. Physical examination revealed central obesity, 'moon'-like face, supraclavicular pads, proximal muscle atrophy, and skin hyperpigmentation. Biochemical and hormonal results were as follows: K 2.3 mmol/L (3.6-5), cortisol 8.00 86 µg/dL (6.2-19.4) 23.00 76 µg/dL, ACTH 8.00 194 pg/mL (7.2-63.3) 23.00 200 pg/mL, DHEAS 330 µg/dL (12-154). CRH stimulation test showed lack of ACTH stimulation > 35%, overnight high dose DST revealed no suppression of cortisol. Chest and abdominal CT as well as somatostatin receptor scan didn't show ectopic tumour responsible for ACTH oversecretion. MRI revealed a pituitary macroadenoma (28 × 20 × 17 mm) extending towards the left cavernous sinus. After partial transsphenoidal adenomectomy, serum cortisol of 40 µg/dL was obtained. The patient's condition was still very poor, so unilateral adrenalectomy was performed. After surgery, serum morning cortisol level dropped to 20 µg/dL and the patient's condition improved significantly. 26 months after the operations, the patient remains in remission. Because her life expectancy exceeds the prognosed duration of remission with the presence of pituitary tumour remnants and intact left adrenal gland, the patient was qualified to radiosurgery with a Gamma Knife. CONCLUSION: In selected cases, unilateral, laparascopic adrenalectomy may serve as a life-saving procedure in a patient with ACTHdependent Cushing's syndrome.

The effect of parathyroid hormones on hair follicle physiology: implications for treatment of chemotherapy-induced alopecia.

Parathyroid hormone (PTH) and parathyroid hormone-related protein (PTHrP) influence hair follicles through paracrine and intracrine routes. There is significant evidence that PTH and PTHrP influence the proliferation and differentiation of hair follicle cells. The PTH/PTHrP receptor signalling plays an important role in the hair follicle cycle and may induce premature catagen-telogen transition. Transgenic mice with an overexpression or blockade (PTH/PTHrP receptor knockout mice) of PTHrP activity revealed impaired or increased hair growth, respectively. Some findings also suggest that PTHrP may additionally influence the hair cycle by inhibiting angiogenesis. Antagonists of the PTH/PTHrP receptor have been shown to stimulate proliferation of hair follicle cells and hair growth. A hair-stimulating effect of a PTH/PTHrP receptor antagonist applied topically to the skin has been observed in hairless mice, as well as in mice treated with cyclophosphamide. These data indicate that the PTH/PTHrP receptor may serve as a potential target for new (topical) hair growth-stimulating drugs, especially for chemotherapy-induced alopecia.

Vitamin D insufficiency in healthy pregnant women living in Warsaw.

BACKGROUND/OBJECTIVES: Ensuring the optimal level of 25-hydroxy-vitamin D (250HD) in serum (concentration above 30 ng/ml) is essential for protecting the health of the mother and the developing fetus. Vitamin D plays an important role in maintaining proper bone structure, preventing infections, reducing the risk of premature birth and gestational diabetes. The aim of the study was to verify whether healthy pregnant residents of Warsaw were deficient in vitamin D. MATERIAL AND METHODS: The material consisted of 150 serum samples of 50 healthy women in 1st, 2nd and 3rd trimester of pregnancy 72.7% of the sera were from women who reported taking multivitamin supplements containing vitamin D3 (71% out of that group was taking 400 IU daily). The concentration of 250HD was measured using the vitamin D total assay on Elecsys 2010 automatic analyzer (Roche Diagnostics). RESULTS: The average serum 250HD concentrations of 50 women in 1st, 2nd and 3rd trimester of pregnancy were respectively: 23.1 ng/ml, 24.8 ng/ml, and 25.1 ng/ml, with no statistically significant differences. The optimal levels of 250HD (30-80 ng/ml) were found in 30.0% of samples, hypovitaminosis (20-30 ng/ml) occurred in 38.7%, deficiency (10-20 ng/ml) in 24.0% and severe deficiency (less than 10 ng/ml) in 7.3% of cases. Mean concentration of 250HD in winter season (October 1 - March 31) was 23.6 ng/ml and in summer season (April 1 - September 30) was 25.5 ng/ml, with no statistically significant difference. On the basis of the BMI in 1st trimester two subgroups were distinguished from the studied subjects: BMI <21 (13 patients, 39 samples) and BMI >25 (14 patients, 42 samples). Mean 250HD concentration in these groups were 27.3 and 23.5 ng/ml respectively (p<0.05). High statistical significance (p<0.001) was found among the total number of samples with 250HD deficiency and severe deficiency (<20 ng/ml) and samples with hypovitaminosis and optimal 250HD level (>20 ng/ml) in these groups. CONCLUSIONS: Regardless of trimester and season, vitamin D below the optimal level is a common occurrence during pregnancy and the current level of supplementation among Polish pregnant women appears to be insufficient. Our data suggest that special attention should be paid to the problem of vitamin D insufficiency in overweight pregnant women.

Can we accurately measure the concentration of clinically relevant vitamin D metabolites in the circulation? The problems and their consequences.

Increased interest in vitamin D measurements in clinical studies has contributed to the development in recent years of several new immunochemical assays (manual and for automatic analyzers). New methods, including HPLC (high performance liquid chromatography), and LC-MS/MS (liquid chromatography coupled with tandem mass spectrometry) have also been introduced into routine diagnostic laboratories. Because of the variety of assays and methods used, the question arises which one is the most accurate for the measurement of vitamin D metabolites concentration. In this review, we summarise the advantages and disadvantages of these methods, describe the complexity of vitamin D metabolites pattern in the circulation, and discuss the problem of accurate measuring its concentration.