Vitamin D and primary hyperparathyroidism (PHPT)

Vitamin D Increases Irisin Serum Levels and the Expression of Its Precursor in Skeletal Muscle

Irisin is a myokine synthesized by skeletal muscle, which performs key actions on whole-body metabolism. Previous studies have hypothesized a relationship between irisin and vitamin D, but the pathway has not been thoroughly investigated. The purpose of the study was to evaluate whether vitamin D supplementation affected irisin serum levels in a cohort of 19 postmenopausal women with primary hyperparathyroidism (PHPT) treated with cholecalciferol for six months. In parallel, to understand the possible link between vitamin D and irisin, we analyzed the expression of the irisin precursor, Fndc5, in the C2C12 myoblast cell line treated with a biologically active form of vitamin D, 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3). Our results demonstrate that vitamin D supplementation resulted in a significant increase in irisin serum levels (p = 0.031) in PHPT patients. In vitro, we show that vitamin D treatment on myoblasts enhanced Fndc5 mRNA after 48 h (p = 0.013), while it increased mRNAs of sirtuin 1 (Sirt1) (p = 0.041) and peroxisome proliferator-activated receptor γ coactivator 1α (Pgc1α) (p = 0.017) over a shorter time course. Overall, our data suggest that vitamin-D-induced modulation of Fndc5/irisin occurs through up-regulation of Sirt1, which together with Pgc1α, is an important regulator of numerous metabolic processes in skeletal muscle.

Evaluation of hemorheological parameters as biomarkers of calcium metabolism and insulin resistance in postmenopausal women

BACKGROUND

Calcium, vitamin D and insulin resistance are linked to osteoporosis and cardiovascular disease in menopause.

OBJECTIVE

Determine if hemorheological parameters related to blood viscosity in microcirculation are linked to calcium metabolism and insulin resistance in menopause.

METHODS

25-Hydroxyvitamin D (25(OH)D)), 1, 25-dihydroxyvitamin D3 (1, 25(OH)2D), parathyroid hormone, ionized calcium, glucose, insulin and hemoglobin A1c were measured in blood from 43 volunteers. Red blood cells (RBC) aggregation, RBC deformability and whole blood viscosity were also performed.

RESULTS

25(OH)D showed a positive correlation with RBC deformability 0.60 Pa. Subjects with 25(OH)D≤29.00 ng/mL had lower RBC deformability 0.60 Pa, and higher RBC aggregation and higher HOMA-IR. Ionized calcium showed a negative correlation with RBC aggregation. Subjects with ionized calcium ≤1.24 mmol/L showed higher RBC aggregation. There was a positive correlation between HOMA-IR and RBC aggregation and HOMA-IR showed a negative correlation with RBC deformability 0.30 Pa. Subjects with HOMA-IR <1.80 showed lower RBC aggregation and higher RBC deformability at 0.30 Pa, 0.60 Pa, 1.20 Pa, 3.0 Pa and 6.0 Pa.

CONCLUSION

Low 25(OH)D, low ionized calcium and high HOMA-IR are related to impaired hemorheology in menopause. RBC aggregation and deformability can be used as biomarkers of calcium metabolism and insulin resistance in menopause.

Role of Vitamin D Supplements in Prevention of Hungry Bone Syndrome after Successful Parathyroidectomy for Primary Hyperparathyroidism: A Prospective Study

BACKGROUND

We postulated that the preoperative correction of vitamin D levels can significantly reduce the incidence of hunger bone syndrome among patients undergoing parathyroidectomy for primary hyperparathyroidism.

METHODS

We performed a prospective, randomized, open-label study on 102 patients with primary hyperparathyroidism and coexisting vitamin D deficiency who were scheduled to undergo parathyroidectomy. Patients were divided into the following two groups: group I which included 52 patients who did not receive preoperative vitamin D supplementation; and group II which included 50 patients who received cholecalciferol 1000-2000 IU daily or 50000 IU weekly until they achieve vitamin D levels >20 ng/mL (group IIa = 25 patients) or vitamin D levels >30 ng/mL (group IIb = 25 patients).

RESULTS

The incidence of hunger bone syndrome in group IIb was lower than group I and group IIa (8% versus 16% versus 23%, respectively); however, this difference did not reach the level of statistical significance (p = 0.22). Patients with hunger bone syndrome were significantly younger and had higher serum phosphorus, alkaline phosphatase, magnesium, and bone mineral density at baseline than patients without hunger bone syndrome. On the other hand, patients with hunger bone syndrome had significantly lower 25-hydroxyvitamin D at baseline than patients without hunger bone syndrome (p = 0.001). The ROC curve showed that the baseline level of serum 25-hydroxyvitamin D was not an independent discriminator of hunger bone syndrome (area under curve = 0.21 (95% CI: 0.06-0.34); p = 0.011).

CONCLUSION

Preoperative course of vitamin D supplements has no preventive role on the postoperative incidence of hunger bone syndrome among patients with primary hyperparathyroidism and coexisting vitamin D deficiency undergoing parathyroidectomy.

Parathormone Levels in a Middle-Eastern Healthy Population Using 2nd and 3rd Generation PTH Assays

BACKGROUND

The purpose of the current study is to determine PTH reference values in vitamin-D-replete Lebanese adults using 2^nd and 3^rd generation PTH assays and to look at the factors that affect PTH variations.

METHODS

Fasting PTH was measured using 2^nd and 3^rd generation Diasorin PTH assays in 339 vitamin-D-replete healthy subjects aged 18 to 63 years (230 men and 109 women) who have normal calcium levels and an eGFR ≥60 ml/mn. 25-OH vitamin D (25(OH)D) was measured using the Diasorin assay.

RESULTS

For the 2^nd PTH generation, median (IQR) levels were 48.9 (34.9-66.0) pg/ml, and its 2.5^th-97.5^th percentile values were 19.7-110.5 pg/ml for 25(OH)D values between 20 and 30 ng/ml, and 19.7-110.7 pg/ml for 25(OH)D values ≥30 ng/ml. For the 3^rd PTH generation, the median (IQR) values were 23.9 (17.7-30.5) pg/ml, and its 2.5^th-97.5^th percentile values were, respectively, 9.2 and 50.2 pg/ml for 25(OH)D values between 20 and 30 ng/ml, and 8.4 and 45.4 pg/ml for 25(OH)D values ≥30 ng/ml. The median (IQR) serum 25(OH)D levels were 27.5 (23.8-32.7) ng/ml. 2^nd and 3^rd generation PTH values are strongly correlated (r = 0.96, p < 0.0001), but poorly concordant (Lin's concordance coefficient 0.365, 95% CI: 0.328-0.401) with observations beyond the 95% Bland-Altman limits of agreement. 2^nd and 3^rd generation PTH levels did not differ according to gender and were significantly correlated with age but not with 25(OH)D and serum calcium levels.

CONCLUSION

Lebanese adult healthy subjects have higher 2^nd and 3^rd generation PTH levels compared with the reference range provided by the manufacturer. The reference range was not influenced by changing the 25(OH)D cutoff. The clinical significance of the higher PTH levels in our population should be investigated.

Parathyroidectomy: is vitamin D a player for a good outcome?

Background: The field of parathyroidectomy (PTx) is complex and brings together many specialists. Even if the surgical approaches changed from classical to minimally invasive PTx, a good outcome is correlated with an adequate localization before and during PTx, while blood assays, such as parathormone (PTH) or 25-hydroxyvitamin D, become useful additional markers. Aim. Specific aspects related to parathyroidectomy and vitamins D (VD) were introduced. Material and Method. The article represents a PubMed-based narrative review. Results. The growing evidence regarding the high prevalence of hypovitaminosis D and early detection of primary hyperparathyroidism (HPT) requires a particular attention to the association of these two disorders, which may be incidental, but some common pathogenic links are displayed. Low VD stimulates PTH production as a secondary or even tertiary type of HPT diagnosis. VD deficiency is associated with larger parathyroid adenomas and higher levels of PTH before and after surgery for primary HPT. Asymptomatically and normocalcemic forms of primary HPT, which are not immediately referred to PTx, require a normalization of the VD levels. VD supplements are safe under some serum calcium cutoffs and offer a better outcome after PTx. However, primary HPT is cured by surgery and, if the indication is well established, this should not be delayed too long to replace VD. Up to half of PTx cases may experience increased PTH levels after surgery, but most of these are transitory if rapid VD correction is done and only a few remaining cases will eventually develop persistent / recurrent primary HPT. Conclusion. A close following of 25-hydroxivitamin D represents one of the keys for a good outcome in the field of parathyroid surgery. Abbreviations: HPT = hyperparathyroidism, MEN = Multiple Endocrine Neoplasia Syndrome, PTx = parathyroidectomy, PTH = parathormone, VD = Vitamin D.

Mechanisms in endocrinology: vitamin D as a potential contributor in endocrine health and disease

OBJECTIVE

It has been suggested that vitamin D may play a role in the pathogenesis of several endocrine diseases, such as hyperparathyroidism, type 1 diabetes (T1DM), type 2 diabetes (T2DM), autoimmune thyroid diseases, Addison's disease and polycystic ovary syndrome (PCOS). In this review, we debate the role of vitamin D in the pathogenesis of endocrine diseases.

METHODS

Narrative overview of the literature synthesizing the current evidence retrieved from searches of computerized databases, hand searches and authoritative texts.

RESULTS

Evidence from basic science supports a role for vitamin D in many endocrine conditions. In humans, inverse relationships have been reported not only between blood 25-hydroxyvitamin D and parathyroid hormone concentrations but also with risk of T1DM, T2DM, and PCOS. There is less evidence for an association with Addison's disease or autoimmune thyroid disease. Vitamin D supplementation may have a role for prevention of T2DM, but the available evidence is not consistent.

CONCLUSIONS

Although observational studies support a potential role of vitamin D in endocrine disease, high quality evidence from clinical trials does not exist to establish a place for vitamin D supplementation in optimizing endocrine health. Ongoing randomized controlled trials are expected to provide insights into the efficacy and safety of vitamin D in the management of endocrine disease.

Subclinical and asymptomatic parathyroid disease: implications of emerging data

Primary hyperparathyroidism, a disorder in which there is a tendency for hypercalcaemia caused by autonomous overproduction of parathyroid hormone, is common, especially in postmenopausal women. Although parathyroidectomy is indicated for symptomatic patients, most individuals with the disorder are asymptomatic and without classic complications, such as renal stones and osteoporosis, at diagnosis. Consensus guidelines suggest which individuals might be suitable for medical follow-up rather than parathyroidectomy, but there are no long-term randomised controlled trials to support the safety of medical surveillance, and some patients progress with time. Data from observational studies suggest that cardiovascular morbidity and mortality are increased in patients with primary hyperparathyroidism, and might be predicted by parathyroid hormone concentrations, even in individuals with asymptomatic primary hyperparathyroidism. Whether parathyroidectomy improves cardiovascular outcomes in patients with asymptomatic primary hyperparathyroidism is unproven, but data suggest that surgery decreases fracture risk and might improve neuropsychological symptoms. Studies also show that patients with normocalcaemic (subclinical) hyperparathyroidism and hypoparathyroidism have a low risk of progression to overt disease, but their long-term risks are not defined. In this Review, we explore the increasing range of asymptomatic parathyroid disorders, focusing on current evidence about their natural history and potential complications, with a particular emphasis on primary hyperparathyroidism.