title: Do current screening recommendations allow for early detection of lithium-induced hyperparathyroidism in patients with bipolar disorder?
abstract: BACKGROUND
  Current screening recommendations for early detection of lithium-associated hyperparathyroidism propose an exclusive measurement of serum albumin-adjusted calcium (Aac) concentration as a single first step. However, longitudinal data in patients with recurrent affective disorders suggest that increases in serum intact parathyroid hormone (iPTH) levels in lithium-treated patients may not necessarily be accompanied by a parallel increase in the concentration of Aac. If true, patients with an isolated increase in iPTH concentration above the reference range might be missed following current screening recommendations. Therefore, this study set out to examine key parameters of calcium metabolism, including iPTH and 25-hydroxycholecalciferol concentrations in patients with bipolar disorder that was or was not managed with lithium.
  
  
  METHODS
  Sixty patients with bipolar disorder according to DSM-IV were enrolled, 30 of whom had received long-term lithium treatment (lithium group), whereas the other 30 patients were on psychopharmacological treatment not including lithium (non-lithium group) at the time of the study. Owing to exclusion criteria (e.g., lithium < 6 months, laboratory results indicative of secondary hyperparathyroidism), 23 bipolar patients composed the final lithium group, whereas 28 patients remained in the non-lithium group for statistical analyses.
  
  
  RESULTS
  Patients in the lithium group showed a significantly higher concentration of iPTH compared to the non-lithium group (p < 0.05). Similarly, Aac concentrations were significantly increased in the lithium group compared to the non-lithium group (p < 0.05). However, in a multivariate linear regression model, group affiliation only predicted iPTH concentration (p < 0.05). In line with this, none of the four patients in the lithium group with an iPTH concentration above the reference range had an Aac concentration above the reference range.
  
  
  CONCLUSIONS
  This study suggests that the biochemical characteristics between primary hyperparathyroidism and lithium-induced hyperparathyroidism differ substantially with regard to regulation of calcium homeostasis. As such, current screening practice does not reliably detect iPTH concentrations above the reference range. Therefore, further research is needed to elucidate the consequences of an isolated iPTH concentration above the reference range in order to develop the most appropriate screening tools for hyperparathyroidism in lithium-treated patients with bipolar disorder.
authors.affiliation: Klinik für Psychiatrie und Psychotherapie, Ludwig-Maximilians Universität München, Nussbaumstrasse 7, Munich, 80336 Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Berger
authors.affiliation: Klinik für Psychiatrie und Psychotherapie, Ludwig-Maximilians Universität München, Nussbaumstrasse 7, Munich, 80336 Germany ; Vinzenz von Paul Hospital, Abt. Psychiatrie, Schwenninger Str. 55, Rottweil, 78628 Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Riedel
authors.affiliation: Klinik für Psychiatrie und Psychotherapie, Ludwig-Maximilians Universität München, Nussbaumstrasse 7, Munich, 80336 Germany ; Isar-Amper Klinikum München, Ost Vockestrasse 72, Haar, 85540 Germany.
authors.forename: Nora
authors.initials: N
authors.lastname: Tomova
authors.affiliation: Klinik für Psychiatrie und Psychotherapie, Ludwig-Maximilians Universität München, Nussbaumstrasse 7, Munich, 80336 Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Obermeier
authors.affiliation: Klinik für Psychiatrie und Psychotherapie, Ludwig-Maximilians Universität München, Nussbaumstrasse 7, Munich, 80336 Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Seemüller
authors.affiliation: Klinik für Psychiatrie und Psychotherapie, Ludwig-Maximilians Universität München, Nussbaumstrasse 7, Munich, 80336 Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: Dittmann
authors.affiliation: Klinik für Psychiatrie und Psychotherapie, Ludwig-Maximilians Universität München, Nussbaumstrasse 7, Munich, 80336 Germany.
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Moeller
authors.affiliation: Klinik und Poliklinik für Psychiatrie und Psychotherapie, Universitätsklinikum Carl Gustav Carus Technische Universität Dresden, Fetscherstr. 74, Dresden, 01307 Germany.
authors.forename: Emanuel
authors.initials: E
authors.lastname: Severus
keywords: Bipolar disorder; Calcium; Hyperparathyroidism; Lithium