Normalization of lithium-induced hypercalcemia and hyperparathyroidism with cinacalcet hydrochloride

Drug-Related Hypercalcemia

This review focuses on the commonly prescribed medicaments that can be responsible for hypercalcemia, considering the prevalence, the predominant pathophysiological mechanisms, and the optimal medical management of each drug-induced hypercalcemia. Vitamin D supplements and 1α-hydroxylated vitamin D analogues increase intestinal calcium absorption, renal calcium reabsorption as well as bone resorption. In patients with hypoparathyroidism receiving recombinant human PTH, transient hypercalcemia can occur because of overtreatment, usually during acute illness. Thiazide-induced hypercalcemia is mainly explained by enhanced renal proximal calcium reabsorption, changing preexistent asymptomatic normocalcemic or intermittently hypercalcemic hyperparathyroidism into the classic hypercalcemic hyperparathyroidism. Lithium causes hypercalcemia mainly by drug-induced hyperparathyroidism.

Lithium-associated hyperparathyroidism

Lithium is a mood stabiliser widely used in the treatment and prophylaxis of mania, bipolar disorders and recurrent depression. Treatment with lithium can give rise to various endocrine and metabolic abnormalities, including thyroid dysfunction, nephrogenic diabetes insipidus and hypercalcaemia. Lithium may induce hypercalcaemia through both acute and chronic effects. The initial acute effects are potentially reversible and occur as a result of lithium's action on the calcium-sensing receptor pathway and glycogen synthase kinase 3, giving rise to a biochemical picture similar to that seen in familial hypocalciuric hypercalcaemia. In the long term, chronic lithium therapy leads to permanent changes within the parathyroid glands by either unmasking hyperparathyroidism in patients with a subclinical parathyroid adenoma or possibly by initiating multiglandular hyperparathyroidism. The latter biochemical picture is identical to that of primary hyperparathyroidism. Lithium-associated hyperparathyroidism, especially in patients on chronic lithium therapy, is associated with increased morbidity. Hence, regular monitoring of calcium levels in patients on lithium therapy is of paramount importance as early recognition of lithium-associated hyperparathyroidism can improve outcomes. This review focuses on the definition, pathophysiology, presentation, investigations and management of lithium-associated hyperparathyroidism.

The role of phospholamban and GSK3 in regulating rodent cardiac SERCA function

Cardiac contractile function is largely mediated by the regulation of Ca²⁺ cycling throughout the lifespan. The sarco(endo)plasmic reticulum Ca²⁺ ATPase (SERCA) pump is paramount to cardiac Ca²⁺ regulation, and it is well established that SERCA dysfunction pathologically contributes to cardiomyopathy and heart failure. Phospholamban (PLN) is a well-known inhibitor of the SERCA pump and its regulation of SERCA2a-the predominant cardiac SERCA isoform-contributes significantly to proper cardiac function. Glycogen synthase kinase 3 (GSK3) is a serine/threonine kinase involved in several metabolic pathways, and we and others have shown that it regulates SERCA function. In this mini-review, we highlight the underlying mechanisms behind GSK3's regulation of SERCA function specifically discussing changes in SERCA2a and PLN expression and its potential protection against oxidative stress. Ultimately, these recent findings that we discuss could have clinical implications in the treatment and prevention of cardiomyopathies and heart failure.

Use of calcimimetics in children with normal kidney function

The calcium-sensing receptor (CaSR) plays an important role in the homeostasis of serum ionized calcium by regulating parathyroid hormone (PTH) secretion and tubular calcium handling. Calcimimetics, which act by allosteric modulation of the CaSR, mimic hypercalcemia resulting in suppression of PTH release and increase in calciuria. Mostly used in children to treat secondary hyperparathyroidism associated with advanced renal failure, we have shown that calcimimetics can also be successfully used in children with bone and mineral disorders in which elevated PTH plays a detrimental role in skeletal pathophysiology in the face of normal kidney function. The current review briefly discusses the role of the CaSR and calcimimetics in calcium homeostasis, and then addresses the potential applications of calcimimetics in children with normal kidney function with disorders in which suppression of PTH is beneficial.

Endocrinological Disorders Related to the Medical Use of Lithium. A Narrative Review

The prescribing of Lithium is common in psychiatric clinical practice. The aim of this study was to identify the most common endocrine side effects associated with this drug and to clarify the pathophysiological basis. A systematic review was conducted in Psycinfo, Embase, PubMed, and Scopus. A computerised search for information was performed using a PICO (patient, intervention, comparative, outcomes) strategy. The main neuroendocrine alterations were reported in kidneys, thyroid and parathyroid glands, pancreas, and the communication pathways between the pituitary and adrenal glands. The pathophysiological mechanisms are diverse, and include the inhibition of the thyroid adenylate cyclase sensitive to the thyroid stimulant hormone (TSH) sensitive adenylate cyclase, which causes hypothyroidism. It also reduces the expression of aquaporin type 2, which is associated with nephrogenic diabetes insipidus, and the loss of the ionic balance of calcium that induces hyperparathyroidism and hypercalcaemia. Other considerations are related to alterations in the hypothalamic-pituitary-adrenal axis and a decrease in the production of catecholamines. Finally, another side-effect is the glycaemic dysregulation caused by the insulin resistance. Periodical clinical and para-clinical evaluations are necessary. The author proposes an evaluation scheme.

Non-surgical management of primary hyperparathyroidism

The purpose of this chapter is to discuss the options available for patients with primary hyperparathyrodism (PHPT) not undergoing parathyroidectomy (PTx). Adequate hydration should be recommended in all patients. Calcium intake should not be restricted and vitamin D deficiency should be corrected aiming at a serum concentration of 25OHD of >20 ng/mL or even higher (>30 ng/mL according to some opinion leaders). Pharmacologic therapy is not an alternative to PTx and could be considered in patients who meet the surgical criteria but unwilling to undergo PTx, as well as in patients with an increased risk of surgery or failed surgery. Targeted therapy includes antiresorptive drugs for skeletal protection and cinacalcet for lowering serum calcium. Combined therapy can be an option when appropriate. Pregnant women should be treated conservatively (hydration) and surgery, if needed, performed in the second trimester of pregnancy. Severe hypercalcemia is a life-threatening condition and requires immediate intensive treatment.

Sporadic multiple parathyroid gland disease--a consensus report of the European Society of Endocrine Surgeons (ESES)

BACKGROUND

Sporadic multiglandular disease (MGD) has been reported in literature in 8-33 % of patients with primary hyperparathyroidism (pHPT). This paper aimed to review controversies in the pathogenesis and management of sporadic MGD.

METHODS

A literature search and review was made to evaluate the level of evidence concerning diagnosis and management of sporadic MGD according to criteria proposed by Sackett, with recommendation grading by Heinrich et al. and Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system. Results were discussed at the 6th Workshop of the European Society of Endocrine Surgeons entitled 'Hyperparathyroidism due to multiple gland disease: An evidence-based perspective'.

RESULTS

Literature reports no prospective randomised studies; thus, a relatively low level of evidence was achieved. Appropriate surgical therapy of sporadic MGD should consist of a bilateral approach in most patients. Unilateral neck exploration guided by preoperative imaging should be reserved for selected patients, performed by an experienced endocrine surgeon and monitored by intraoperative parathormone assay (levels of evidence III-V, grade C recommendation). There is conflicting or equally weighted levels IV-V evidence supporting that cure rates can be similar or worse for sporadic MGD than for single adenomas (no recommendation). Best outcomes can be expected if surgery is performed by an experienced parathyroid surgeon working in a high-volume centre (grade C recommendation). Levels IV-V evidence supports that recurrent/persistence pHPT occurs more frequently in patients with double adenomas hence in situations where a double adenoma has been identified, the surgeon should have a high index of suspicion during surgery and postoperatively for the possibility of a four-gland disease (grade C recommendation).

CONCLUSIONS

Identifying preoperatively patients at risk for MGD remains challenging, intraoperative decisions are important for achieving acceptable cure rates and long-term follow-up is mandatory in such patients.

Long-term outcome after parathyroidectomy for lithium-induced hyperparathyroidism

BACKGROUND

The accepted management of lithium-associated hyperparathyroidism (LiHPT) is open four-gland parathyroid exploration (OPTX). This approach has recently been the subject of controversy. A recent study has shown very high long-term recurrence rates after OPTX, whereas some have promoted unilateral focused parathyroidectomy as appropriate management. The aim was to evaluate long-term outcomes after surgery for LiHPT and to assess the accuracy of preoperative imaging.

METHODS

This was a retrospective cohort study that comprised all patients undergoing initial surgery for LiHPT between 1990 and 2013. The cumulative recurrence rate was calculated by the Kaplan-Meier method. The sensitivity and specificity of sestamibi scintigraphy and ultrasound imaging for identification of single-gland versus multigland disease was investigated using intraoperative assessment as reference.

RESULTS

Of 48 patients, 45 had OPTX and three underwent focused parathyroidectomy. Multiglandular disease was documented in 27 patients and 21 had a single adenoma. The median follow-up was 5·9 (range 0·3-22) years and 16 patients died during follow-up. The 10-year cumulative recurrence rate was 16 (95 per cent confidence interval 2 to 29) per cent. No permanent complications occurred after primary surgery for LiHPT. Twenty-four patients had at least one preoperative ultrasound or sestamibi scan. For concordant sestamibi scintigraphy and ultrasound imaging, the sensitivity and specificity for identifying single-gland versus multigland disease was five of nine and five of eight respectively.

CONCLUSION

Surgery provided a safe and effective management option for patients with LiHPT in this series, with a long-term cure rate of well over 80 per cent.

Hypercalcemia in patients with bipolar disorder treated with lithium: a cross-sectional study

BACKGROUND

Lithium-induced hyperparathyroidism (LIH) is a relative underrecognized complication of long-term lithium treatment. Hypercalcemia may be the first, but often overlooked, sign of LIH. Symptoms of LIH can be similar to the underlying psychiatric illness, which may cause a significant doctor's delay in diagnosing LIH. The aim of this study was to determine the prevalence of hypercalcemia in a cohort of psychiatric patients.

METHODS

In this cross-sectional study, we collected data from 314 patients treated with lithium in an outpatient clinic for bipolar disorder. Patients with bipolar disorder from the same clinics, who had never been treated with lithium and of whom serum calcium levels were available, were included as controls (n = 15). Patient characteristics and laboratory results were collected during the period of June 2010 till June 2011.

RESULTS

The mean serum calcium level was 2.49 (SD 0.11) mmol/l. The point prevalence of hypercalcemia (>2.60 mmol/l) was 15.6%. In a comparable group of psychiatric patients not using lithium, the mean serum calcium level was 2.37 mmol/l, and none of these patients had hypercalcemia (p = 0.001). The duration of lithium treatment was the only significant predictor for the development of hypercalcemia (p = 0.002).

DISCUSSION

The prevalence of hypercalcemia in lithium-treated patients was significantly higher than that in non-lithium treated controls and correlated to the cumulative time lithium was used in this cross-sectional study. We recommend that serum calcium levels should be routinely tested in patients using lithium for timely detection of LIH or hypercalcemia due to other causes.

Do current screening recommendations allow for early detection of lithium-induced hyperparathyroidism in patients with bipolar disorder?

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.

Discussion

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.

Lithium-associated hypercalcemia and hyperparathyroidism in the elderly: what do we know?

BACKGROUND

Lithium has been reported to induce hypercalcemia and hyperparathyroidism, yet few studies have examined the impact on older patients. We therefore undertook this review and report our findings.

METHOD

We undertook a systematic review of articles on lithium-associated hypercalcemia and/or hyperparathyroidism that were identified via electronic English language database searches through PubMed.

RESULTS

Among reported cases and case series of lithium-associated hyperparathyroidism in which ages of specific subjects were provided, 40% of affected individuals were over age 60. Mean serum calcium levels are reported to be higher in lithium treated patients over age 60 compared with younger patients. While many patients who develop lithium-associated hypercalcemia and hyperparathyroidism are asymptomatic, symptomatic complications may be more of a concern in older patients, especially in those with co-morbid renal disease.

LIMITATIONS

To date, all cross-sectional studies of lithium-associated hypercalcemia and hyperparathyroidism are of mixed age group cohorts and more specific studies focused on older patients have yet to be performed.

CONCLUSIONS

Lithium-induced hypercalcemia and hyperparathyroidism are under-recognized potential complications of lithium therapy which may occur more frequently in older patients. Psychiatrists should be vigilant in screening for hypercalcemia and hyperparathyroidism in their older patients receiving lithium, both prior to starting treatment and at least annually thereafter.

Endocrine disturbances related to the use of lithium

Despite recent advances in pharmacological treatment of psychiatric disorders, lithium salts remain frequently used, as they are effective and inexpensive alternatives, especially in the treatment of bipolar disorders. Their use is commonly associated with various endocrine disorders, mainly in thyroid and parathyroid function, and in mineral metabolism. This article aims at reviewing these potential endocrinopathies related to the use of lithium to make health care professionals aware and familiar with these possible complications when they follow up patients using this drug, and to make them able to monitor, identify and institute early and appropriate treatment.

Lithium-associated hyperparathyroidism: surgical strategies in the era of minimally invasive parathyroidectomy

BACKGROUND

Lithium remains an effective treatment of bipolar affective disorder. The long-term use of lithium is associated with an alteration in parathyroid function that may culminate in hyperparathyroidism. The long-term effects of lithium use are variable due to its complex effects on calcium homeostasis and bone metabolism, and as a consequence the indications for surgery remain poorly defined. The optimal surgical strategy for lithium-associated hyperparathyroidism in the era of minimally invasive surgery is also the subject of debate. The aim of the present study was to evaluate the variable findings of lithium-associated parathyroid disease.

METHODS

A retrospective review was performed of patients undergoing parathyroid surgery presenting with lithium-associated hyperparathyroidism from July 1999 until July 2009 at the university hospital La Timone, Marseille, and from October 2005 to July 2009 at Hammersmith Hospital, Imperial College, London. Fifteen patients underwent surgery for lithium-associated hyperparathyroidism. Clinical data including patient demographics, duration of lithium use, clinical manifestations of hyperparathyroidism, indications for surgery, and biochemical parameters preoperatively and postoperatively were reviewed. Preoperative imaging, the surgical procedure performed, operative findings, and histopathology were also analyzed.

RESULTS

All 15 patients had preoperative imaging: sestamibi scanning showed that 10 patients had localized single-gland disease, 1 had multiple hot spots, and 4 had a negative scan. Ultrasonography demonstrated a single abnormal gland in 8 patients and multiple enlarged glands in 1 patient; the test was negative in 6. As a consequence of concordant preoperative imaging a minimally invasive approach (endoscopic or a focused lateral approach) was adopted in 3 patients. Focused surgery demonstrated an enlarged hyperplastic gland in 3 cases and resulted in normocalcemia in the immediate postoperative period. However, one patient has a serum calcium at the upper limit of normal and elevated parathyroid hormone (PTH) levels, suggestive of possible recurrence of disease at 15 months follow-up. One patient has permanent hypoparathyroidism. In those patients who had open procedures, final histology showed hyperplastic multiglandular disease in 10 patients (83.3%) of patients and single-gland disease in 2 patients (16.7%). None of these patients show evidence of recurrence at follow-up.

CONCLUSIONS

Lithium hyperparathyroidism is predominantly a multiglandular disease characterized by asymmetrical hyperplasia that is frequently associated with misleading or discordant localization studies. Bilateral neck exploration is therefore recommended in order to minimize the risk of disease recurrence.

Cinacalcet in the management of primary hyperparathyroidism

Parathyroidectomy is currently the only curative treatment for primary hyperparathyroidism (PHPT). There are few alternative treatment options in patients who are ineligible for, or unwilling to undergo, surgery and those in whom parathyroidectomy has failed. Current options include the recently approved drug cinacalcet. Cinacalcet is an allosteric modulator of the calcium-sensing receptor, acting to sensitize this receptor to extracellular calcium. Cinacalcet has been found to be effective in reducing or normalizing serum calcium levels in several groups of PHPT patients, including those with mild-to-moderate PHPT, intractable disease, parathyroid carcinoma and multiple endocrine neoplasia Type 1. Cinacalcet slightly reduces parathyroid hormone levels and has no effect on bone mineral density. Cinacalcet is well tolerated when used at low doses, but side effects are not uncommon when relatively high doses are needed to control hypercalcemia. The current evidence indicates that cinacalcet may be of benefit in a wide spectrum of PHPT severities, offering a novel therapeutic option for the control of hypercalcemia in PHPT patients who are not able to undergo parathyroidectomy. It is presently unknown how much of the biochemical benefit of cinacalcet treatment translates into a clinical benefit, particularly in patients with mild-to-moderate hypercalcemia. Moreover, there are no data as to whether long-term treatment with cinacalcet can prevent the complications of PHPT.

New concepts in calcium-sensing receptor pharmacology and signalling

The calcium-sensing receptor (CaR) is the key controller of extracellular calcium (Ca(2+)(o)) homeostasis via its regulation of parathyroid hormone (PTH) secretion and renal Ca(2+) reabsorption. The CaR-selective calcimimetic drug Cinacalcet stimulates the CaR to suppress PTH secretion in chronic kidney disease and represents the world's first clinically available receptor positive allosteric modulator (PAM). Negative CaR allosteric modulators (NAMs), known as calcilytics, can increase PTH secretion and are being investigated as possible bone anabolic treatments against age-related osteoporosis. Here we address the current state of development and clinical use of a series of positive and negative CaR modulators. In addition, clinical CaR mutations and transgenic mice carrying tissue-specific CaR deletions have provided a novel understanding of the relative functional importance of CaR in both calciotropic tissues and those elsewhere in the body. The development of CaR-selective modulators and signalling reagents have provided us with a more detailed appreciation of how the CaR signals in vivo. Thus, both of these areas of CaR research will be reviewed.

Update on the use of cinacalcet in the management of primary hyperparathyroidism

Cinacalcet is an allosteric modulator of the calcium sensing receptor acting to sensitize this receptor to the extracellular calcium. Cinacalcet has been shown to be effective in reducing or normalizing serum calcium levels in several groups of patients with primary hyperparathyroidism (PHPT), including patients with mild to moderate PHPT, intractable PHPT, and parathyroid carcinoma, and in PHPT as a part of multiple endocrine neoplasia type 1. Cinacalcet slightly reduces PTH levels and has no effects on bone mineral density. Cinacalcet at low doses is well tolerated, but side effects are more frequent and severe when relatively high doses are needed to control hypercalcemia. Cinacalcet may be of benefit in a wide spectrum of PHPT severity, offering a novel therapeutic option for the control of hypercalcemia in PHPT patients who are not able to undergo parathyroidectomy. To what extent the reduction of serum calcium particularly in patients with mild to moderate hypercalcemia, translates into a clinical benefit is currently unknown. Moreover, there are no data as to whether long-term treatment with cinacalcet can prevent the complications of PHPT. Finally, more data are needed on the long-term safety of cinacalcet, particularly at the renal level.

Lithium therapy and hyperparathyroidism: an evidence-based assessment

BACKGROUND

Prolonged therapeutic exposure to lithium compounds can have adverse consequences on calcium homeostasis. A unique form of hyperparathyroidism appears to be causally linked to chronic lithium exposure. We provide a comprehensive review of relevant literature using a structured, evidence-based approach.

METHODS

Published data were identified from systematic electronic literature searches. References are assigned a level of evidence according to a validated classification schema.

RESULTS

Level III and V evidence supports an etiologic link between sustained lithium therapy and both hypercalcemia and hyperparathormonemia (grade C recommendation). Level V evidence supports the use of preoperative parathyroid imaging if a focused exploration is planned (grade C recommendation). Level V evidence supports the use of intraoperative parathyroid hormone monitoring to guide appropriate surgical therapy (grade C recommendation). There is conflicting and equally weighted level V evidence supporting a routine preoperative plan of bilateral neck exploration versus selective unilateral exploration (no recommendation). There may be a role for calcimimetic drug therapy as an alternate, nonsurgical means of controlling lithium-associated hyperparathyroidism (grade C recommendation).

CONCLUSIONS

Evidence-based recommendations support screening of patients on chronic lithium therapy for hypercalcemia. Appropriate surgical therapy may consist of either a bilateral or a unilateral approach when performed by an experienced endocrine surgeon. Focused approaches should be guided by preoperative imaging and intraoperative hormone monitoring. Calcimimetic therapy is a potential alternative to parathyroidectomy.

Long-term results of surgery for lithium-associated hyperparathyroidism

BACKGROUND

Lithium therapy for affective bipolar disease is frequently associated with hyperparathyroidism (HPT), but the results of surgical treatment are virtually unknown. The aim of this retrospective review was to analyse the long-term outcome after surgery for lithium-induced HPT in a large series of patients.

METHODS

Seventy-one patients on chronic lithium therapy who underwent surgery in three university and three district hospitals in Sweden were followed for a median of 6.3 years. Histopathology, complications of surgery and normocalcaemia at 6 months after surgery and last follow-up were analysed.

RESULTS

The primary histopathological diagnoses were adenoma (45 per cent), double adenomas (3 per cent) and hyperplasia (52 per cent). No permanent paresis of the recurrent laryngeal nerve was recorded but 13 per cent of the patients suffered from permanent hypoparathyroidism. At follow-up, the rate of persistent and recurrent HPT was 42 per cent regardless of the histopathological diagnosis.

CONCLUSION

The results of conventional surgery for lithium-associated HPT are poor. The surgical approach should be adjusted for the multiglandular disease that is usually the cause of HPT in patients on chronic lithium therapy.

Clinical utility of calcimimetics targeting the extracellular calcium-sensing receptor (CaSR)

Calcimimetics, which activate the extracellular calcium (Ca(o)(2+))-sensing receptor in the parathyroid and other tissues participating in Ca(o)(2+) homeostasis, were the first described allosteric activators of a G-protein-coupled receptor. Cinacalcet, the only calcimimetic currently approved for human use, is used clinically for treating secondary hyperparathyroidism (e.g., overactivity of parathyroid glands) in patients being dialyzed for chronic kidney disease. By sensitizing the parathyroids to Ca(o)(2+), cinacalcet lowers the circulating parathyroid hormone (PTH) level. It also reduces serum calcium and phosphate, changes increasing the percentage of patients achieving the guidelines recommended by the National Kidney Foundation (NKF) for these minerals. Studies are underway addressing whether better adherence to these guidelines in patients receiving cinacalcet reduces cardiovascular disease and related mortality, which are both common is the dialysis population. The second approved use of cinacalcet is for treating hypercalcemia in patients with inoperable parathyroid carcinoma. In this setting, it provides the first medical therapy chronically lowering serum calcium concentration in this condition, albeit not to normal in most patients. Its effect on the long-term prognosis of these patients, if any, is presently unclear. "Off-label" administration of cinacalcet [i.e., not yet approved by the US Food and Drug Administration (FDA)] effectively lowers serum calcium and/or PTH in various other forms of hyperparathyroidism and increases serum phosphate in renal phosphate-wasting syndromes by reducing PTH-induced phosphaturia. In the future, the drug could conceivably be utilized to modulate the activity of the CaSR in other tissues (i.e., kidney, colon) in therapeutically desirable ways.

Physiology and pathophysiology of the calcium-sensing receptor in the kidney

The extracellular calcium-sensing receptor (CaSR) plays a major role in the maintenance of a physiological serum ionized calcium (Ca2+) concentration by regulating the circulating levels of parathyroid hormone. It was molecularly identified in 1993 by Brown et al. in the laboratory of Dr. Steven Hebert with an expression cloning strategy. Subsequent studies have demonstrated that the CaSR is highly expressed in the kidney, where it is capable of integrating signals deriving from the tubular fluid and/or the interstitial plasma. Additional studies elucidating inherited and acquired mutations in the CaSR gene, the existence of activating and inactivating autoantibodies, and genetic polymorphisms of the CaSR have greatly enhanced our understanding of the role of the CaSR in mineral ion metabolism. Allosteric modulators of the CaSR are the first drugs in their class to become available for clinical use and have been shown to treat successfully hyperparathyroidism secondary to advanced renal failure. In addition, preclinical and clinical studies suggest the possibility of using such compounds in various forms of hypercalcemic hyperparathyroidism, such as primary and lithium-induced hyperparathyroidism and that occurring after renal transplantation. This review addresses the role of the CaSR in kidney physiology and pathophysiology as well as current and in-the-pipeline treatments utilizing CaSR-based therapeutics.

Adverse endocrine and metabolic effects of psychotropic drugs: selective clinical review

The article critically reviews selected, clinically significant, adverse endocrine and metabolic effects associated with psychotropic drug treatments, including hyperprolactinaemia, hyponatraemia, diabetes insipidus, hypothyroidism, hyperparathyroidism, sexual dysfunction and virilization, weight loss, weight gain and metabolic syndrome (type 2 diabetes mellitus, dyslipidaemia and hypertension). Such effects are prevalent and complex, but can be managed clinically when recognized. They encourage continued critical assessment of benefits versus risks of psychotropic drugs and underscore the importance of close coordination of psychiatric and general medical care to improve long-term health of psychiatric patients. Options for management of hyperprolactinaemia include lowering doses, switching to agents such as aripiprazole, clozapine or quetiapine, managing associated osteoporosis, carefully considering the use of dopamine receptor agonists and ruling out stress, oral contraceptive use and hypothyroidism as contributing factors. Disorders of water homeostasis may include syndrome of inappropriate antidiuretic hormone (SIADH), managed by water restriction or slow replacement by hypertonic saline along with drug discontinuation. Safe management of diabetes insipidus, commonly associated with lithium, involves switching mood stabilizer and consideration of potassium-sparing diuretics. Clinical hypothyroidism may be a more useful marker than absolute cut-offs of hormone values, and may be associated with quetiapine, antidepressant and lithium use, and managed by thyroxine replacement. Hyper-parathyroidism requires comprehensive medical evaluation for occult tumours. Hypocalcaemia, along with multiple other psychiatric and medical causes, may result in decreased bone density and require evaluation and management. Strategies for reducing sexual dysfunction with psychotropics remain largely unsatisfactory. Finally, management strategies for obesity and metabolic syndrome are reviewed in light of the recent expert guidelines, including risk assessment and treatments, such as monoamine transport inhibitors, anticonvulsants and cannabinoid receptor antagonists, as well as lifestyle changes.

Appropriate surgical treatment of lithium-associated hyperparathyroidism

BACKGROUND

Lithium is frequently used in the treatment of bipolar disease. Although lithium-associated hyperparathyroidism (LAH) is well documented, reports concerning its pathologic findings are sparse. Because of a high-reported incidence of multiglandular disease, focused exploration for LAH is controversial.

METHODS

From 1995 to 2007, data from 1207 consecutive patients who underwent concise parathyroid exploration for sporadic primary hyperparathyroidism (PHP) directed by quick intraoperative parathyroid hormone monitoring (QPTH) were reviewed to identify patients with LAH. Anatomic findings were determined. All patients had >5 months of follow-up.

RESULTS

The incidence of LAH was 16/1207 (1.3%). The rate of multiglandular disease was not higher in LAH: present in 25% (4/16) patients with LAH and 12.3% (146/1191) patients without LAH (p = 0.13 Fisher two-tailed test). Among 16 patients with LAH, 12 (75%) had a single adenoma. The use of QPTH allowed unilateral exploration in 8 of 12 patients with single adenoma. Parathyroid exploration resulted in durable biochemical cure for all 16 patients with LAH.

CONCLUSION

Multiglandular disease seems to be no more frequent in patients with LAH than in patients with primary hyperparathyroidism (PHP) without LAH. Patients with LAH can be safely and effectively managed with selective unilateral exploration directed by intraoperative PTH monitoring.

Lithium nephrotoxicity revisited

Lithium is widely used to treat bipolar disorder. Nephrogenic diabetes insipidus (NDI) is the most common adverse effect of lithium and occurs in up to 40% of patients. Renal lithium toxicity is characterized by increased water and sodium diuresis, which can result in mild dehydration, hyperchloremic metabolic acidosis and renal tubular acidosis. The concentrating defect and natriuretic effect develop within weeks of lithium initiation. After years of lithium exposure, full-blown nephropathy can develop, which is characterized by decreased glomerular filtration rate and chronic kidney disease. Here, we review the clinical and experimental evidence that the principal cell of the collecting duct is the primary target for the nephrotoxic effects of lithium, and that these effects are characterized by dysregulation of aquaporin 2. This dysregulation is believed to occur as a result of the accumulation of cytotoxic concentrations of lithium, which enters via the epithelial sodium channel (ENaC) on the apical membrane and leads to the inhibition of signaling pathways that involve glycogen synthase kinase type 3beta. Experimental and clinical evidence demonstrates the efficacy of the ENaC inhibitor amiloride for the treatment of lithium-induced NDI; however, whether this agent can prevent the long-term adverse effects of lithium is not yet known.

Hypercalcemia

Laboratory reports of elevated serum calcium are common in both inpatient and outpatient settings. Distinguishing between measurements likely to cause symptoms and that require correction from those that are benign poses a challenge to the physician. Calcium stores, serum measurement, and regulation are reviewed as an introduction to understanding the etiology and treatment of hypercalcemia.

Hypercalcemia and diabetes insipidus in a patient previously treated with lithium

BACKGROUND

A 65-year-old woman presented with decreased oral intake, a reduced level of consciousness, hypercalcemia and hypernatremia. She had previously received lithium for 20 years for a schizoaffective disorder, but this treatment had been discontinued 3 years before presentation.

INVESTIGATIONS

Physical examination, laboratory studies including measurement of serum calcium and parathyroid hormone levels, measurement of urine and serum osmolalities before and after desmopressin administration, blood and urine cultures, and a CT scan of the abdomen.

DIAGNOSIS

Urosepsis, dehydration, kidney stone disease, hyperparathyroidism, and nephrogenic diabetes insipidus.

MANAGEMENT

Hydration, antibiotics, intravenous pamidronate for rapid control of hypercalcemia, parathyroidectomy, surgical removal of the large kidney stones, a low-protein and low-sodium diet, and initiation of treatment with a thiazide diuretic.