title: Estimation of magnesium in patients with functional hypoparathyroidism.
abstract: BACKGROUND
  It is evident that about 30-50% of patients with Vitamin D deficiency (VDD) do not manifest develop secondary hyperparathyroidism (SHPT). A number of theories have been proposed to explain this lack of SHPT, including hypomagnesemia.
  
  
  METHODS
  Retrospective review of laboratory database.
  
  
  METHODS
  We evaluated the differences in serum magnesium (Mg) levels among those with VDD with or without SHPT. A retrospective review of 6255 laboratory data of bone mineral profiles performed in the period of 2007-2013. After excluding patients with hypercalcemia, renal dysfunction/unknown kidney function and primary hypothyroidism, the remaining 1323 patient data were analyzed. SHPT was defined as serum parathyroid hormone >65 in those with VDD.
  
  
  METHODS
  ANOVA and Wilcoxon tests as appropriate to compare means. Multivariate logistic regression to analyze relation between variables and outcome of SHPT.
  
  
  RESULTS
  We noted that 55% patients (n = 727) had VDD, and among those who had VDD, 23% (n = 170) were hypocalcemic (corrected serum calcium <8.5). Patients with VDD who did not exhibit SHPT were 56% (n = 407). The mean (±standard deviation) serum Mg levels in the entire cohort (n = 1323) was 1.94 ± 0.26 mg/dl and 1.95 ± 0.26 mg/dl in VDD cohort and 2 ± 0.31 mg/dl in the VDD-hypocalcemic cohort. There was no statistical difference in the Mg levels among those with SHPT compared to those without SHPT (P = 0.14). Serum calcium and phosphorus were lower in those with SHPT (P = 0.06 and P < 0.001, respectively). In multivariate logistic regression, serum calcium (P = 0.043), phosphorus (P < 0.001) and severe VDD (P < 0.001) independently correlated with occurrence of SHPT in VDD.
  
  
  CONCLUSIONS
  Serum Mg levels did not explain the functional hypoparathyroidism seen in about half of the patients with VDD. A low normal serum calcium and phosphorus levels are more likely to be associated with VDD patients who develop SHPT.
authors.affiliation: Department of Endocrinology, Diabetology and Bariatric Medicine, Narayana Health City, Bengaluru, Karnataka, India.
authors.forename: Subramanian
authors.initials: S
authors.lastname: Kannan
authors.affiliation: Department of Endocrinology, Sri Ramachandra Medical College, Porur, Tamil Nadu, India.
authors.forename: Shriraam
authors.initials: S
authors.lastname: Mahadevan
authors.affiliation: Kovai Medical Centre and Hospital, Coimbatore, Tamil Nadu, India.
authors.forename: P
authors.initials: P
authors.lastname: Velayutham
authors.affiliation: Department of Endocrinology, Chettinad Medical College, Madurai, Tamil Nadu, India.
authors.forename: R
authors.initials: R
authors.lastname: Bharath
authors.affiliation: Alpha Hospital and Research Centre, Madurai, Tamil Nadu, India.
authors.forename: V
authors.initials: V
authors.lastname: Kumaravel
authors.affiliation: Arka Center for Hormonal Health, Adyar, Chennai, Tamil Nadu, India.
authors.forename: J
authors.initials: J
authors.lastname: Muthukumaran
authors.affiliation: SKS Hospital, Salem, Tamil Nadu, India.
authors.forename: A
authors.initials: A
authors.lastname: Premkumar
keywords: Calcium; Vitamin D deficiency; hyperparathyroidism; magnesium; phosphorus