Estimation of magnesium in patients with functional hypoparathyroidism

Investigation of hypomagnesaemia prevalence and underlying aetiology in a hospitalised cohort of dogs with ionised hypocalcaemia

OBJECTIVES

Calcium is the most abundant mineral in the body and plays a critical role in a wide range of physiological processes. Low concentrations of ionised calcium, the most metabolically available form of calcium, have been linked to an increased risk of adverse clinical outcomes in dogs. Magnesium plays an important role in parathyroid hormone function. The objective of this study was to define the prevalence and aetiology of hypomagnesaemia in a hospitalised cohort of dogs with ionised hypocalcaemia (IHC).

METHODS

A total magnesium reference interval was established using serum biochemistry results from 346 clinically healthy dogs. The clinical records of dogs with IHC were reviewed, and concurrent serum magnesium concentrations were recorded alongside clinical signs and underlying aetiology. The prevalence, clinical presentation and aetiology of hypomagnesaemia were examined in the IHC population.

RESULTS

Two hundred and ninety-five IHC dogs were identified. Hypomagnesaemia was identified in 22%. Total magnesium concentration was significantly higher in dogs with renal disease. The most common cause of concurrent hypomagnesaemia and IHC was gastrointestinal diseases.

CONCLUSION

Low concentrations of serum magnesium occur in approximately one fifth of all dogs with IHC. Further studies are required to clarify the link between magnesium status, IHC and clinical outcome.

Prevalence and Determinants of a Blunted Parathyroid Hormone Response in Young Saudi Women with Vitamin D Deficiency: A Cross-Sectional Study

Vitamin D deficiency is highly prevalent among the Saudi population. Increased parathyroid hormone (PTH) secretion is an appropriate homeostatic response to correct the resultant hypocalcemia. However, not all vitamin D deficiency patients have increased PTH levels. This study determined the prevalence of a blunted PTH response to vitamin D deficiency among apparently healthy young Saudi women and assessed anthropometric and biochemical factors associated with this response by performing a secondary analysis of data obtained from a cross-sectional study conducted at the "Center of Excellence for Osteoporosis research." Overall, 315 women (aged 20-45 years) with vitamin D deficiency (serum 25-hydroxyvitamin D (25(OH)D) levels <30 nmol/L) were included. They were divided into two groups according to the laboratory cutoff value of PTH (<7 or ≥7 pmol/L), and anthropometric and biochemical characteristics of both groups were compared. Women with a blunted PTH response (n = 62, 19.7%) had a significantly lower body mass index (BMI) (P < 0.001) and smaller waist circumference (P=0.001). They also had significantly higher serum 25(OH)D (P=0.001), corrected serum calcium (P < 0.001), and phosphate (P=0.003) levels than those with an elevated PTH response (n = 253, 80.3%). Multiple logistic regression analysis showed that lower BMI (OR = 0.925; 95% CI: 0.949-0.987) and higher 25(OH)D (OR = 1.068; 95% CI: 1.014-1.124) and serum calcium (OR = 8.600; 95% CI: 1.614-45.809) levels were significantly associated with a blunted PTH response (R ² = 0.178). A blunted PTH response to vitamin D deficiency is mainly observed among women with lower BMI. Higher serum calcium and 25(OH)D levels and lower BMI were significant predictors of a blunted PTH response, which may indicate that these subjects are adapting to lower 25(OH)D levels and maintaining normal calcium levels without the need to increase PTH secretion. The mechanisms underlying this adaptation are unclear, and future studies to explore these mechanisms are warranted.

Effects of Elevated Parathyroid Hormone Levels on Muscle Health, Postural Stability and Quality of Life in Vitamin D-Insufficient Healthy Women: A Cross-Sectional Study

Independently of plasma 25-hydroxyvitamin D (P-25(OH)D) levels, elevated parathyroid hormone (PTH) levels may exert an adverse effect on muscle health, postural stability, well-being, and quality of life. Using a cross-sectional design, we investigated 104 healthy postmenopausal women with low P-25(OH)D (< 50 nmol/l) levels, who had either secondary hyperparathyroidism (SHPT) with elevated PTH levels (> 6.9 pmol/l, n = 52) or normal PTH levels (n = 52). The average PTH value in women with SHPT was 8.5 (interquartile range 7.5-9.7) pmol/l and 5.3 (4.4-6.3) pmol/l in women with normal PTH (p < 0.001). Plasma phosphate was significantly lower in women with SHPT than in women with normal PTH (1.01 ± 0.14 vs. 1.09 ± 0.13 mmol/l; p < 0.01). In the total cohort, average level of 25(OH)D were 38 (31-45) nmol/l, with no differences between groups. SHPT was associated with impaired muscle strength as assessed by both maximum muscle strength and maximum force production at knee flexion with the knee fixed at 60° and 90° (p_all < 0.05). Postural stability was impaired during semi tandem standing (p = 0.001). However, the two groups did not differ in terms of self-reported physical activity, muscle-related symptoms, quality of life, or lean muscle mass as assessed by dual-energy X-ray absorptiometry. Independently of 25(OH)D levels, mild to moderately elevated PTH levels are associated with adverse effects on muscle strength and postural stability. Why some individuals respond to vitamin D insufficiency with an elevated PTH and others do not need further elucidation, but elevated PTH itself seems to affect muscle function and postural stability.

Parathyroid hormone response to different vitamin D levels in population-based old and very-old Polish cohorts

BACKGROUND

Low vitamin D (VD) is not always followed by the development of secondary hyperparathyroidism (SHPT). The study aimed to assess the prevalence of SHPT and functional hypoparathyroidism (FHPT) in relation to VD deficiency/insufficiency and factors predisposing to parathyroid hormone (PTH) response in old and very-old Caucasians.

METHODS

A sub-study of the cross-sectional PolSenior project analyzed serum 25(OH)D, intact PTH (iPTH) and C-terminal fibroblast growth factor 23 (cFGF23) concentrations in 3472 (1658 women) individuals aged ≥65 years. SHPT was defined as iPTH concentration > 65 pg/mL, while FHPT as iPTH within the reference range in the presence of 25(OH)D < 30 ng/mL.

RESULTS

SHPT was diagnosed in 426 participants (14%) and was more frequent in very-old (≥ 80 years) than in the old (65-79 years) subgroup (18.8 vs 9.8%; OR = 2.12; 95% CI: 1.72-2.62). While, FHPT was found in 2269 subjects (85.2%) with 25(OH)D < 30 ng/mL, and was more prevalent in the old than very-old subgroup (89.3 vs 80.1%; OR = 2.03; 95% CI: 1.63-2.52). Multiple regression analysis showed that age ≥ 80 years, use of loop diuretics, decreased glomerular filtration rate, higher cFGF23 level but lower calcium and phosphate concentrations, predispose for the occurrence of SHPT.

CONCLUSIONS

The interrelation between 25(OH)D deficiency and PTH response is complex. In older adults, PTH response is related to VD deficiency, age, impaired kidney function, the use of loop diuretics and the levels of calcium, phosphate, and cFGF23.

General anesthesia for patient with Fahr's syndrome: A case report

RATIONALE

Fahr's syndrome (FS) is a rare neurological and psychiatric disorder characterized by bilateral brain calcifications when a secondary cause of the calcification is found.

PATIENT CONCERNS

A 53-year-old female patient diagnosed with FS for laminectomy because of ossification of posterior longitudinal ligament. She had a history of generalized tonic-clonic (GTC) seizure and medication with anticonvulsant drugs. She had gait disturbance, spasticity, bradykinesia, and diffuse calcifications in the basal ganglia, thalamus, cerebellum, and cerebral hemispheres on the brain computed tomography. On the preoperative examination, the serum and ionized calcium (Ca) were decreased to 3.7 and 2.22 mg/dL. Hypomagnesemia is combined with hypocalcemia. Furthermore, the level of parathyroid hormone was decreased to 2.18 pg/mL.

DIAGNOSES

Due to the radiologic findings and laboratory test results, she was diagnosed with FS with primary hypoparathyroidism.

INTERVENTIONS

The Ca and magnesium (Mg) had been corrected before surgery but the electrolytes revealed low level at the intraoperative period. The 300 mg of calcium chloride was administered at 2 times and 1200 mg of it were infused for 1 hour during intraoperative periods. In addition, total 4 g of Mg sulfate intravenously administered. We used rocuronium as a neuromuscular block and checked neuromuscular function by train-of-four monitoring.

OUTCOMES

Residual neuromuscular blockade was reversed with pyridostigmine and her muscle power completely recovered. The patient was extubated successfully and no unpredictable events occurred. On the day following transfer, serum electrolytes remained low, and although Ca was continuously supplied, serum Ca did not recover to a normal level. The patient was medicated with anticonvulsant drugs but experienced GTC seizure 2 weeks after surgery.

LESSONS

We presume that the pathophysiology of FS was related to primary hypoparathyroidism and hypomagnesemia. FS raises concerns associated with neuromuscular problems, spasticity, and seizure, and concerns of hypotension, heart failure, cardiac arrhythmia, and cerebrovascular attack during perioperative periods, among anesthesiologists because of hypocalcemia and vessel calcification. During the perioperative period, Ca levels should be closely monitored, and titrated Ca replacement therapy is recommended. The simultaneous correction of hypomagnesemia is of considerable importance when correcting hypocalcemia.

Bone metabolism, density, and geometry in postmenopausal women with vitamin D insufficiency: a cross-sectional comparison of the effects of elevated parathyroid levels

Increased levels of parathyroid hormone (PTH) may have adverse effects on bone health. In a cross-sectional design, we investigated this hypothesis among 102 postmenopausal vitamin D insufficient women. Elevated PTH was associated with altered bone geometry, decreased bone mineral density in the spine, and increased bone turnover.

INTRODUCTION

In vitamin D insufficiency, elevated parathyroid hormone (PTH) levels may contribute to adverse effect on bone. We assessed effects of PTH responses to vitamin D insufficiency on bone metabolism, density, and geometry.

METHODS

Using a cross-sectional design, we investigated 102 healthy postmenopausal women with low 25-hydroxy-vitamin D (< 50 nmol/L) levels, who had either secondary hyperparathyroidism with elevated PTH levels (> 6.9 pmol/L, N = 51) or normal PTH levels (N = 51). Bone mineral density (BMD) and bone geometry were assessed by Dual-Energy X-ray absorptiometry (DXA), quantitative computed tomography (QCT) and high-resolution peripheral QCT (HRpQCT) scans. Bone metabolism was assessed by biochemistry including bone turnover markers.

RESULTS

Levels of 25(OH)D were 38 (IQR 31-45) nmol/L with no differences between groups. PTH levels were 8.5 (IQR 7.5-9.5) in women with SHPT and 5.2 (4.4-6.6) pmol/L in women with normal PTH (p < 0.001). BMI and eGFR did not differ between groups. SHPT was associated with lower total- and trabecular bone area, lower cortical perimeter, and increased cortical area in tibia and radius. SHPT was associated with a lower weight-adjusted BMD at the lumbar spine (p < 0.05). High compared to normal PTH levels were associated with significantly lower plasma levels of 1,25(OH)₂D, phosphate, but higher levels of osteocalcin and borderline higher levels of CTx. PTH correlated to osteocalcin and CTx.

CONCLUSIONS

High PTH levels are associated with altered bone geometry, increased bone turnover, and reduced BMD at the spine. Whether an increased cortical thickness with a lower trabecular volume is an effect of PTH or not needs further elucidations.

European Society of Endocrinology Clinical Guideline: Treatment of chronic hypoparathyroidism in adults

Hypoparathyroidism (HypoPT) is a rare (orphan) endocrine disease with low calcium and inappropriately low (insufficient) circulating parathyroid hormone levels, most often in adults secondary to thyroid surgery. Standard treatment is activated vitamin D analogues and calcium supplementation and not replacement of the lacking hormone, as in other hormonal deficiency states. The purpose of this guideline is to provide clinicians with guidance on the treatment and monitoring of chronic HypoPT in adults who do not have end-stage renal disease. We intend to draft a practical guideline, focusing on operationalized recommendations deemed to be useful in the daily management of patients. This guideline was developed and solely sponsored by The European Society of Endocrinology, supported by CBO (Dutch Institute for Health Care Improvement) and based on the Grading of Recommendations Assessment, Development and Evaluation (GRADE) principles as a methodological base. The clinical question on which the systematic literature search was based and for which available evidence was synthesized was: what is the best treatment for adult patients with chronic HypoPT? This systematic search found 1100 articles, which was reduced to 312 based on title and abstract. The working group assessed these for eligibility in more detail, and 32 full-text articles were assessed. For the final recommendations, other literature was also taken into account. Little evidence is available on how best to treat HypoPT. Data on quality of life and the risk of complications have just started to emerge, and clinical trials on how to optimize therapy are essentially non-existent. Most studies are of limited sample size, hampering firm conclusions. No studies are available relating target calcium levels with clinically relevant endpoints. Hence it is not possible to formulate recommendations based on strict evidence. This guideline is therefore mainly based on how patients are managed in clinical practice, as reported in small case series and based on the experiences of the authors.