Parathyroid hormone therapy for hypoparathyroidism

The calcium-sensing receptor: a comprehensive review on its role in calcium homeostasis and therapeutic implications

The calcium-sensing receptor (CaSR), a key member of the family C G protein-coupled receptors (GPCRs), plays a crucial role in regulating calcium homeostasis and parathyroid hormone (PTH) secretion. It responds to various physiological ligands, including calcium ions and amino acids, activating multiple signaling pathways through interactions with different G proteins and β-arrestin. This review focuses on the structural features of CaSR, emphasizing recent advances in understanding its activation mechanisms via agonists and allosteric modulators. CaSR holds significant therapeutic potential, particularly in treating calcitropic disorders such as hyperparathyroidism and hypoparathyroidism. Current pharmacological agents, including calcimimetics such as cinacalcet and etelcalcetide, have proven effective in managing secondary hyperparathyroidism (SHPT); however, they are associated with side effects such as hypocalcemia. Emerging investigational drugs, including palopegteriparatide and other small molecules, show promise in addressing various calcium-related conditions. Despite challenges that have led to the discontinuation of some drug developments, ongoing research is focused on refining CaSR-targeted therapies to improve efficacy, reduce adverse effects, and enhance patient outcomes.

Parathyroid allotransplantation for severe post-surgical hypoparathyroidism: a Brazilian experience

This study presents the cases of two women who developed severe permanent hypoparathyroidism after neck surgery for papillary thyroid cancer and underwent parathyroid allotransplantation. Despite taking high doses of calcium and calcitriol supplements, the patients experienced persistent hypocalcemic symptoms. Fresh parathyroid tissue was removed and prepared from two patients with hyperparathyroidism secondary to end-stage kidney disease and was implanted in the non-dominant forearm of the recipients. Donors and recipients were ABO-compatible, and immunological screening was performed only in Case 2 (HLA typing, panel reactive antibody, and crossmatch tests). A short-term immunosuppressive regimen was adopted, consisting of 3 days of methylprednisolone followed by 7 days of prednisone. In Case 1, oral supplementation decreased to half of the initial dose 1 month after transplantation and to one-fifth at the end of a 12-month follow-up period. In Case 2, intravenous calcium was discontinued 1-week post-transplantation, with no need for its use during the 12-month follow-up period. Serum parathyroid hormone levels did not increase and remained undetectable in both cases. In contrast, serum calcium levels increased significantly, and both patients experienced relief from hypocalcemic symptoms. Parathyroid allotransplantation can be an effective and safe treatment for PH and should be considered in severe cases. Nevertheless, formal recommendations depend on additional studies and validated protocols.

Forestalling Hungry Bone Syndrome after Parathyroidectomy in Patients with Primary and Renal Hyperparathyroidism

Hungry bone syndrome (HBS), severe hypocalcemia following parathyroidectomy (PTX) due to rapid drop of PTH (parathormone) after a previous long term elevated concentration in primary (PHPT) or renal hyperparathyroidism (RHPT), impairs the outcome of underlying parathyroid disease.

OBJECTIVE

overview HBS following PTx according to a dual perspective: pre- and post-operative outcome in PHPT and RHPT. This is a case- and study-based narrative review.

INCLUSION CRITERIA

key research words "hungry bone syndrome" and "parathyroidectomy"; PubMed access; in extenso articles; publication timeline from Inception to April 2023.

EXCLUSION CRITERIA

non-PTx-related HBS; hypoparathyroidism following PTx. We identified 120 original studies covering different levels of statistical evidence. We are not aware of a larger analysis on published cases concerning HBS (N = 14,349). PHPT: 14 studies (N = 1545 patients, maximum 425 participants per study), and 36 case reports (N = 37), a total of 1582 adults, aged between 20 and 72. Pediatric PHPT: 3 studies (N = 232, maximum of 182 participants per study), and 15 case reports (N = 19), a total of 251 patients, aged between 6 and 18. RHPT: 27 studies (N = 12,468 individuals, the largest cohort of 7171) and 25 case reports/series (N = 48), a total of 12,516 persons, aged between 23 and 74. HBS involves an early post-operatory (emergency) phase (EP) followed by a recovery phase (RP). EP is due to severe hypocalcemia with various clinical elements (<8.4 mg/dL) with non-low PTH (to be differentiated from hypoparathyroidism), starting with day 3 (1 to 7) with a 3-day duration (up to 30) requiring prompt intravenous calcium (Ca) intervention and vitamin D (VD) (mostly calcitriol) replacement. Hypophosphatemia and hypomagnesiemia may be found. RP: mildly/asymptomatic hypocalcemia controlled under oral Ca+VD for maximum 12 months (protracted HBS is up to 42 months). RHPT associates a higher risk of developing HBS as compared to PHPT. HBS prevalence varied from 15% to 25% up to 75-92% in RHPT, while in PHPT, mostly one out of five adults, respectively, one out of three children and teenagers might be affected (if any, depending on study). In PHPT, there were four clusters of HBS indicators. The first (mostly important) is represented by pre-operatory biochemistry and hormonal panel, especially, increased PTH and alkaline phosphatase (additional indicators were elevated blood urea nitrogen, and a high serum calcium). The second category is the clinical presentation: an older age for adults (yet, not all authors agree); particular skeleton involvement (level of case reports) such as brown tumors and osteitis fibrosa cystica; insufficient evidence for the patients with osteoporosis or those admitted for a parathyroid crisis. The third category involves parathyroid tumor features (increased weight and diameter; giant, atypical, carcinomas, some ectopic adenomas). The fourth category relates to the intra-operatory and early post-surgery management, meaning an associated thyroid surgery and, maybe, a prolonged PTx time (but this is still an open issue) increases the risk, as opposite to prompt recognition of HBS based on calcium (and PTH) assays and rapid intervention (specific interventional protocols are rather used in RHPT than in PHPT). Two important aspects are not clarified yet: the use of pre-operatory bisphosphonates and the role of 25-hydroxyitamin D assay as pointer of HBS. In RHPT, we mentioned three types of evidence. Firstly, risk factors for HBS with a solid level of statistical evidence: younger age at PTx, pre-operatory elevated bone alkaline phosphatase, and PTH, respectively, normal/low serum calcium. The second group includes active interventional (hospital-based) protocols that either reduce the rate or improve the severity of HBS, in addition to an adequate use of dialysis following PTx. The third category involves data with inconsistent evidence that might be the objective of future studies to a better understanding; for instance, longer pre-surgery dialysis duration, obesity, an elevated pre-operatory calcitonin, prior use of cinalcet, the co-presence of brown tumors, and osteitis fibrosa cystica as seen in PHPT. HBS remains a rare complication following PTx, yet extremely severe and with a certain level of predictability; thus, the importance of being adequately identified and managed. The pre-operatory spectrum of assessments is based on biochemistry and hormonal panel in addition to a specific (mostly severe) clinical presentation while the parathyroid tumor itself might provide useful insights as potential risk factors. Particularly in RHPT, prompt interventional protocols of electrolytes surveillance and replacement, despite not being yet a matter of a unified, HBS-specific guideline, prevent symptomatic hypocalcemia, reduce the hospitalization stay, and the re-admission rates.

Efficacy and Safety of Parathyroid Hormone Replacement With TransCon PTH in Hypoparathyroidism: 26-Week Results From the Phase 3 PaTHway Trial

Conventional therapy for hypoparathyroidism consisting of active vitamin D and calcium aims to alleviate hypocalcemia but fails to restore normal parathyroid hormone (PTH) physiology. PTH replacement therapy is the ideal physiologic treatment for hypoparathyroidism. The double-blind, placebo-controlled, 26-week, phase 3 PaTHway trial assessed the efficacy and safety of PTH replacement therapy for hypoparathyroidism individuals with the investigational drug TransCon PTH (palopegteriparatide). Participants (n = 84) were randomized 3:1 to once-daily TransCon PTH (initially 18 μg/d) or placebo, both co-administered with conventional therapy. The study drug and conventional therapy were titrated according to a dosing algorithm guided by serum calcium. The composite primary efficacy endpoint was the proportion of participants at week 26 who achieved normal albumin-adjusted serum calcium levels (8.3-10.6 mg/dL), independence from conventional therapy (requiring no active vitamin D and ≤600 mg/d of calcium), and no increase in study drug over 4 weeks before week 26. Other outcomes of interest included health-related quality of life measured by the 36-Item Short Form Survey (SF-36), hypoparathyroidism-related symptoms, functioning, and well-being measured by the Hypoparathyroidism Patient Experience Scale (HPES), and urinary calcium excretion. At week 26, 79% (48/61) of participants treated with TransCon PTH versus 5% (1/21) wiplacebo met the composite primary efficacy endpoint (p < 0.0001). TransCon PTH treatment demonstrated a significant improvement in all key secondary endpoint HPES domain scores (all p < 0.01) and the SF-36 Physical Functioning subscale score (p = 0.0347) compared with placebo. Additionally, 93% (57/61) of participants treated with TransCon PTH achieved independence from conventional therapy. TransCon PTH treatment normalized mean 24-hour urine calcium. Overall, 82% (50/61) treated with TransCon PTH and 100% (21/21) wiplacebo experienced adverse events; most were mild (46%) or moderate (46%). No study drug-related withdrawals occurred. In conclusion, TransCon PTH maintained normocalcemia while permitting independence from conventional therapy and was well-tolerated in individuals with hypoparathyroidism. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Is parathyroid allotransplantation a viable option in the treatment of permanent hypoparathyroidism? A review of the literature

BACKGROUND

The standard clinical treatment for hypoparathyroidism, replacement of calcium and vitamin metabolites (calcitriol), has been used for decades; however, evidence points to its inefficiency in acting on the pathophysiology of the disease, which may precipitate or aggravate conditions already related to hypoparathyroidism. Therapies based on recombinant human parathyroid hormone have emerged in recent years but still have low availability due to their high cost. Parathyroid allotransplantation (Pt-a) has been reported as a strategy for treating more severe cases.

METHODS

This narrative review highlights relevant aspects of conventional permanent hypoparathyroidism treatment and provides a comprehensive and critical review of the reports of applications of Pt-a, especially those carried out in recent years. Particular focus is placed on the following key points: parathyroid immunogenicity, immunosuppression regimens (short-term or chronic), techniques to reduce the expression of immunogenic molecules, follow-up time, and reductions in calcium and vitamin D supplementation.

CONCLUSION

Pt-a has been considered a safe and relatively low-cost therapy and is believed to have the potential to cure the disease, in addition to treating symptoms. However, there is considerable heterogeneity in treatment protocols; therefore, more studies are required to improve the standardization of the procedure and thus improve the consistency of outcomes.

Treatment options in hypoparathyroidism

Hypoparathyroidism remains the single endocrine deficiency disease that is not habitually treated with the missing hormone. In this article, we aim to provide a review of the conventional approach and the novel therapies as well as an overview of the perspectives on the treatment of this rare condition. We conducted a literature review on the conventional therapy using vitamin D analogs and calcium salts, indications for thiazide diuretics and phosphorus binders, PTH analogs history and usage, and the drugs that are currently being tested in clinical trials. Conventional treatment involves calcium salts and vitamin D analogs. Thiazide diuretics can be used to reduce hypercalciuria in some cases. A low-phosphate diet is recommended, and phosphate binders are rarely needed. During pregnancy, a careful approach is necessary. The use of PTH analogs is a new approach despite the limitation of high cost. Studies have included modified PTH molecules, calcilytics, microencapsulation of human parathyroid cells, and allotransplantation.

Skeletal abnormalities in Hypoparathyroidism and in Primary Hyperparathyroidism

Both hypoparathyroidism (HypoPT), as well as its pathological counterpart, primary hyperparathyroidism (PHPT), can lead to skeletal abnormalities. Chronic deficiency of PTH in patients with HypoPT is associated with a profound reduction in bone remodeling, with consequent increases in bone density, and abnormalities in microarchitecture and bone strength. It is still not clear whether there is an increase in fracture risk in HypoPT. While standard therapy with calcium supplements and active vitamin D does not restore bone homeostasis, treatment of HypoPT with PTH appears to correct some of those abnormalities. In PHPT, the continuous exposure to high levels of PTH causes an increase in bone remodeling, in which bone resorption prevails. In the symptomatic form of PHPT, patients can present with fragility fractures, and/or the classical radiological features of osteitis fibrosa cystica. However, even in mild PHPT, catabolic skeletal actions of PTH are evident through reduced BMD, deterioration of bone microarchitecture and increased risk of fragility fractures. Successful parathyroidectomy improves skeletal abnormalities. Medical treatment, such as bisphosphonates and denosumab, can also increase bone density in patients with PHPT who do not undergo surgery. This article reviews skeletal involvement in HypoPT and in PHPT, as assessed by bone remodeling, DXA, trabecular bone score, and quantitative computed tomography, as well as data on bone strength and fracture risk. The effects of PTH replacement on the skeleton in subjects with HypoPT, and the outcome of parathyroidectomy in patients with PHPT, are also reviewed here.

Hypoparathyroidism in Pregnancy and Lactation: Current Approach to Diagnosis and Management

Background: Hypoparathyroidism is an uncommon endocrine disorder. During pregnancy, multiple changes occur in the calcium-regulating hormones, which may affect the requirements of calcium and active vitamin D during pregnancy in patients with hypoparathyroidism. Close monitoring of serum calcium during pregnancy and lactation is ideal in order to optimize maternal and fetal outcomes. In this review, we describe calcium homeostasis during pregnancy in euparathyroid individuals and also review the diagnosis and management of hypoparathyroidism during pregnancy and lactation. Methods: We searched the MEDLINE, CINAHL, EMBASE, and Google scholar databases from 1 January 1990 to 31 December 2020. Case reports, case series, book chapters, and clinical guidelines were included in this review. Conclusions: During pregnancy, rises in 1,25-dihydroxyvitamin D (1,25-(OH)2-D3) and PTH-related peptide result in suppression of PTH and enhanced calcium absorption from the bowel. In individuals with hypoparathyroidism, the requirements for calcium and active vitamin D may decrease. Close monitoring of serum calcium is advised in women with hypoparathyroidism with adjustment of the doses of calcium and active vitamin D to ensure that serum calcium is maintained in the low-normal to mid-normal reference range. Hyper- and hypocalcemia should be avoided in order to reduce the maternal and fetal complications of hypoparathyroidism during pregnancy and lactation. Standard of care therapy consisting of elemental calcium, active vitamin D, and vitamin D is safe during pregnancy.

Postoperative Chronic Hypoparathyroidism and Quality of Life After Total Thyroidectomy

Chronic hypoparathyroidism (HypoPT) is a common complication after total thyroidectomy and it impacts affected patients' quality of life (QoL). This study aimed to assess the QoL in patients with chronic HypoPT independently from their concurrent hypothyroidism and other comorbidities. For this purpose a follow‐up study was performed, including 14 patients who developed chronic HypoPT after total thyroidectomy and 28 age‐ and sex‐matched patients who had intact parathyroid function after total thyroidectomy. We used the RAND Short Form 36 Health Survey (SF‐36) to compare the QoL between patients with or without chronic HypoPT. Chronic HypoPT patients had lower QoL scores in all domains of the RAND‐SF‐36 questionnaire and significant impairment in six of eight domains after adjustment for relevant confounders. They were more often operated because of a toxic diagnosis (p = .01), often being Graves disease. Additionally adjusting for surgical indications resulted in three of eight domains being significant affected. Chronic HypoPT is associated with significantly impairment of QoL, independently of the concurrent disease of hypothyroidism, comorbidities, and prospective values of TSH and serum (se)‐ionized‐Ca⁺⁺. There is a need for more focus and better treatment of patients experiencing chronic HypoPT after surgery. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Inactivation of parathyroid hormone: perspectives of drug discovery to combating hyperparathyroidism

Hormonal coordination is tightly regulated within the human body and thus regulates human physiology. The parathyroid hormone (PTH), a member of the endocrine system, regulates the calcium and phosphate level within the human body. Under non-physiological conditions, PTH levels get upregulated (hyperparathyroidism) or downregulated (hypoparathyroidism) due to external or internal factors. In the case of hyperparathyroidism, elevated PTH stimulates cellular receptors present in the bones, kidneys, and intestines to increase the blood calcium level, leading to calcium deposition. This eventually causes various symptoms including kidney stones. Currently, there is no known medication that directly targets PTH in order to suppress its function. Therefore, it is of great interest to find novel small molecules or any other means that can modulate PTH function. The molecular signaling of PTH starts by binding of its N-terminus to the G-protein coupled PTH1/2 receptor. Therefore, any intervention that affects the N-terminus of PTH could be a lead candidate for treating hyperparathyroidism. As a proof-of-concept, there are various possibilities to inhibit molecular PTH function by (i) a small molecule, (ii) N-terminal PTH phosphorylation, (iii) fibril formation and (iv) residue-specific mutations. These modifications put PTH into an inactive state, which will be discussed in detail in this review article. We anticipate that exploring small molecules or other means that affect the N-terminus of PTH could be lead candidates in combating hyperparathyroidism.

Characteristics of hypoparathyroidism in Colombia: data from a single center in the city of Medellín

OBJECTIVE

Hypoparathyroidism is a rare condition, whose most common etiology is complications of neck surgery. The aim of the study was to identify the clinical and biochemical profile of the patients with diagnosis of hypoparathyroidism, including the frequency of symptoms, clinical signs, long-term complications and disease control. Additionally, the study sought to know what the medication profile was, and the doses required by the patients.

SUBJECTS AND METHOD

A retrospective cohort study was conducted wherein all patients with ICD-10 codes associated with hypoparathyroidism between 2011 and 2018 at the Hospital Universitario San Vicente Fundación were included. We investigated the etiology of the disease; biochemical profile including lowest serum calcium, highest serum phosphorus, 25OHD levels, calciuria and calcium/phosphorus product; medication doses, disease control, and presence of complications, especially renal and neurologic complications were also evaluated.

RESULTS

The cohort included 108 patients (99 women/9 men) with a mean age of 51.6 ± 15.6 years. The main etiology was postoperative (93.5%), the dose of elemental calcium received was relatively low (mean 1,164 mg/day), and in only 9.2% of cases more than 2,500 mg/day of elemental calcium was necessary. We were able to evaluate the follow-up in 89 patients, and found that only 57.3% met the criteria for controlled disease.

CONCLUSION

The clinical profile of patients with hypoparathyroidism in our cohort is similar to that described in other international studies, with predominantly postoperative etiology. With standard therapy, only adequate control is achieved in a little more than half of patients. Arch Endocrinol Metab. 2020;64(3):282-9.

Postoperative Hypoparathyroidism: Prognosis, Prevention, and Treatment (Review)

This review summarizes the results of studies concerning the problem of post-surgical hypoparathyroidism, a common complication of thyroid gland surgery, decreasing the quality of life in patients and, in some cases, leading to disability. A search for publications was carried out in electronic databases Web of Science, Scopus, Academic Search Complete (EBSCO), eLIBRARY, using keywords. The search depth was 7-10 years. Prevalence of post-surgical hypoparathyroidism was evaluated, the pathogenetic causes of the disease development, its clinical forms, methods of diagnosis and treatment were studied. It has been found that there is no single algorithm for analyzing the prognostic factors for the development of this pathological condition. It is emphasized that drug therapy of post-surgical hypoparathyroidism has a number of adverse effects. Therefore, the issues of prevention and surgical correction are of particular relevance. However, controversial opinions of contemporary authors about their clinical effectiveness determine the scientific and practical significance of further research on these issues.

Afebrile Seizures as Initial Symptom of Hypocalcemia Secondary to Hypoparathyroidism

Hypocalcemia is rare in childhood and caused, among other conditions, by hypoparathyroidism. DiGeorge syndrome is the most common cause of hypoparathyroidism in childhood. Presentation of a rare cause of hypocalcemia in childhood and the necessity of measuring serum electrolyte levels in patients presenting with afebrile seizures. a 7.5-year-old female child presented with afebrile seizures lasting 5 min with postictal drowsiness. A similar episode 1 month ago is described. On admission, a positive Trousseau sign, papilledema, and long QTc on electrocardiography were detected. Laboratory testing revealed hypocalcemia, increased creatine phosphokinase and phosphate levels, decreased levels of parathormone, with normal thyroid function and normal levels of blood gases. considering the diagnosis of hypoparathyroidism possible, we started on calcium gluconate solution 5% intravenously and calcium carbonate per os. 48 h later, the child transferred to tertiary hospital for further evaluation. The laboratory findings revealed 25-OH Vitamin D deficiency with normal cortisol levels and the absence of autoantibodies. Kidney and brain imaging and also the electroencephalogram were normal. Calcium carbonate, magnesium, and Vitamin D were administered per os. The child discharged from hospital with complete resolution of symptoms. Since then, she is in treatment with calcium carbonate and Vitamin D per os. Hypoparathyroidism is rare in childhood. We underline the necessity of measuring serum electrolyte levels in patients presenting with afebrile seizures.

Long-term outcomes and management considerations after parathyroidectomy in the dialysis patient

Parathyroidectomy (PTX) remains an important intervention for dialysis patients with poorly controlled secondary hyperparathyroidism (SHPT), though there are only retrospective and observational data that show a mortality benefit to this procedure. Potential consequences that we seek to avoid after PTX include persistent or recurrent hyperparathyroidism, and parathyroid insufficiency. There is considerable subjectivity in defining and diagnosing these conditions, given that we poorly understand the optimal PTH targets (particularly post PTX) needed to maintain bone and vascular health. While lowering PTH after PTX decreases bone turnover, long-term changes in bone activity have been poorly explored. High turnover bone disease, usually present at the time a PTX is considered, often swings to a state of low turnover in the setting of sufficiently low PTH levels. It remains unclear if all low bone turnover equate with disease. However, such changes in bone turnover appear to predispose to vascular calcification, with positive calcium balance after PTX being a potential contributor. We know little of how the post-PTX state resets calcium balance, how calcium and VDRA requirements change or what kind of adjustments are needed to avoid calcium loading. The current consensus cautions against excessive reduction of PTH although there is insufficient evidence-based guidance regarding the management of chronic kidney disease - mineral bone disease (CKD-MBD) parameters in the post-PTX state. This article aims to compile existing research, provide an overview of current practice with regard to PTX and post-PTX chronic management. It highlights gaps and controversies and aims to re-orient the focus to clinically relevant contemporary priorities in CKD-MBD management after PTX.

Increased mortality and morbidity in patients with chronic hypoparathyroidism: A population-based study

OBJECTIVES

A population-based study was undertaken to determine the mortality and morbidity for people with hypoparathyroidism compared to the general population.

METHODS

In this study, patients identified with chronic hypoparathyroidism using data linkage from regional datasets were compared with five age- and gender-matched controls from the general population. Data from biochemistry, hospital admissions, prescribing and the demographic dataset were linked. Outcomes for mortality and specified conditions were examined for all patients and subdivided into post-surgical and non-surgical cases of hypoparathyroidism.

RESULTS

All patients had an increased risk of epilepsy (HR 1.65 [95% CI 1.12-2.44]) and cataracts (HR 2.10 [1.30-3.39]) but no increased fracture risk. Only non-surgical hypoparathyroid patients also had increased mortality (HR 2.11 [1.49-2.98]), cardiovascular disease (HR 2.18 [1.41-3.39]), cerebrovascular disease (HR 2.95 [1.46-5.97]), infection (HR 1.87 [1.2-2.92]) and mental illness (HR 1.59 [1.21-2.11]). There was an increased risk of renal failure (HR 10.05 [95% CI 4.71-21.43]) during the first 2000 days (5.5 years) of follow-up. Renal failure and death were associated with increasing serum calcium concentrations.

CONCLUSION

Patients with hypoparathyroidism have an increased risk of cataract and epilepsy. Non-surgical hypoparathyroidism is associated with increased mortality and additional morbidities.

Current treatment of hypoparathyroidism: Theory versus reality waiting guidelines for children and adolescents

The diagnosis of hypoparathyroidism(HPT)is readily made in the presence of hypocalcemia with markedly reduced or absent parathormone (PTH) levels. Currently available treatments for HPT include high dose vitamin D (ergocalciferol, D2 and cholecalciferol, D3) or, the active metabolite dihydroxy vitamin D (calcitriol), in addition to calcium supplements.This regimen, if not well monitored, can lead to hypercalciuria, as PTH deficiency impairs renal calcium reabsorption. Thus the goal of treatment, is to maintain serum calcium at the low end of the normal range. Undertreatment can cause symptomatic hypocalcemia, while overtreatment hypercalciuria, which may lead to nephrolithiasis, nephrocalcinosis, and renal insufficiency. At present, there is no consensus on the management of HPT in children and adolescents and only few studies are available on the long term outcome of patients with recombinant HPT treatment. The purpose of this article is to review, in a comprehensive manner, the major aspects of HPT management in children and adolescents waiting for authoritative guidelines for the treatment of HPT in this group of patients. Further research, addressing specific questions for this population are urgently needed to improve long-term safety of patients. Educational interventions are also needed for professionals, parents and patients to enable them to improve knowledge, quality of life and effective management care at home. (www.actabiomedica.it)

A Population-Based Study of the Epidemiology of Chronic Hypoparathyroidism

There are very few reports on the epidemiology of chronic hypoparathyroidism. A population-based study was undertaken to describe the prevalence and incidence of hypoparathyroidism in Tayside, Scotland. Data on biochemistry, hospital admissions, prescribing, and death records in Tayside, Scotland, from 1988 to 2015 were linked electronically. Patients with at least three serum albumin-corrected calcium concentrations below the reference range that were taken in an outpatient setting were included in the study. Patients with severe chronic kidney disease before low calcium were excluded from the study. Patients with hypocalcemia were included if they had either previous neck surgery/irradiation, a low serum parathyroid hormone (PTH), or were treated with vitamin D. Patients were identified as having either a postsurgical or a nonsurgical cause or had secondary hypoparathyroidism, eg, hypomagnesemia. Overall, 18,955 patients were identified with hypocalcemia. Of these, 222 patients had primary hypoparathyroidism, 116 with postsurgical and 106 with nonsurgical chronic hypoparathyroidism. In 2015, the prevalence of primary hypoparathyroidism was 40 per 100,000, with a rate of 23 and 17 per 100,000, respectively, for postsurgical and nonsurgical. Eighty percent of the former and 64% of the latter were female. The mean serum calcium at diagnosis was 1.82 mmol/L (SD ± 0.24) and the annual incidence varied from 1-4 per 100,000. Overall, 71% of patients were prescribed vitamin D and/or calcium, whereas activated vitamin D was used in 48% of postsurgical cases and 43% of nonsurgical cases. Thyroxine and/or hydrocortisone were prescribed in more than 90% of postsurgical and 64% of nonsurgical cases. In conclusion, the prevalence of nonsurgical chronic hypoparathyroidism was greater than previously reported using this population-based approach. Many had mild hypocalcemia and did not receive any treatment. © 2017 American Society for Bone and Mineral Research.

Diagnosis and treatment of hypoparathyroidism: a position statement from the Brazilian Society of Endocrinology and Metabolism

Objective To present an update on the diagnosis and treatment of hypoparathyroidism based on the most recent scientific evidence. Materials and methods The Department of Bone and Mineral Metabolism of the Sociedade Brasileira de Endocrinologia e Metabologia (SBEM; Brazilian Society of Endocrinology and Metabolism) was invited to prepare a document following the rules set by the Guidelines Program of the Associação Médica Brasileira (AMB; Brazilian Medical Association). Relevant papers were retrieved from the databases MEDLINE/PubMed, LILACS, and SciELO, and the evidence derived from each article was classified into recommendation levels according to scientific strength and study type. Conclusion An update on the recent scientific literature addressing hypoparathyroidism is presented to serve as a basis for the diagnosis and treatment of this condition in Brazil.

Teriparatide Replacement Therapy for Hypoparathyroidism During Treatment With Lenvatinib for Advanced Thyroid Cancer: A Case Report

Thyroid cancer metastasizes in 4% of cases. Approximately two-thirds of these patients are refractory to radioactive iodine-131 (RAI) therapy and have a poor 10-year survival prognosis. Treatment with tyrosine kinase inhibitors (TKIs) may be administered in selected RAI-refractory patients. However, these agents are often associated with adverse events, including vomiting. We report the case of a patient affected by RAI-refractory thyroid cancer with lung and intracranial metastases undergoing treatment with the antiangiogenic TKI lenvatinib, and with teriparatide replacement therapy for postsurgical hypoparathyroidism. Due to lenvatinib-related vomiting, which did not respond to therapy, conventional oral calcium supplementation failed to maintain normal serum calcium levels and the patient had repeated episodes of hypocalcemia. Subcutaneous teriparatide injections restored serum calcium levels, and thus lenvatinib therapy could be continued. This experience indicates that hormone replacement with teriparatide is a feasible option for cancer patients affected by hypoparathyroidism not treatable with oral calcium supplementation.

Hypoparathyroidism: disease update and new methods of treatment

Гипопаратиреоз характеризуется гипокальциемией при нормальном или низком уровне паратиреоидного гормона (ПТГ). ПТГ регулирует уровень кальция в крови, влияя на реабсорбцию кальция и фосфора в почках, а также витамин D-зависимое всасывание кальция из желудочно-кишечного тракта. Наиболее распространенной причиной гипопаратиреоза является повреждение околощитовидных желез в ходе хирургического вмешательства в области шеи, в основном по поводу заболеваний щитовидной железы. Стандартные методы лечения включают в себя назначение препаратов кальция и витамина D для поддержания уровня кальция на нижней границе референсного интервала с целью предупреждения гиперкальциурии. Однако в ряде случаев компенсация гипокальциемии требует использования высоких доз препаратов кальция и витамина D, что сопровождается выраженным колебанием уровня кальция крови, внескелетной кальцификацией и ухудшением функции почек. В настоящее время наиболее перспективным методом лечения гипопаратиреоза является заместительная терапия рекомбинантным человеческим ПТГ(1-84), который представляет собой полноразмерный ПТГ. ПТГ(1-84) способствует поддержанию стойкой нормокальциемии, улучшая качество жизни пациентов. Однако влияние ПТГ(1-84) на функцию почек, костный обмен и профилактику других осложнений гипопаратиреоза требует дальнейшего изучения.

Hypoparathyroidism: Less Severe Hypocalcemia With Treatment With Vitamin D2 Compared With Calcitriol

Context

Options for chronic treatment of hypoparathyroidism include calcitriol, recombinant human parathyroid hormone, and high-dose vitamin D (D2). D2 is used in a minority of patients because of fear of prolonged hypercalcemia and renal toxicity. There is a paucity of recent data about D2 use in hypoparathyroidism.

Objective

Compare renal function, hypercalcemia, and hypocalcemia in patients with hypoparathyroidism treated chronically with either D2 (D2 group) or calcitriol.

Design, Setting, and Patients

A retrospective study of patients with hypoparathyroidism treated at the University of Maryland Hospital. Participants were identified by a billing record search with diagnosis confirmed by chart review. Thirty patients were identified; 16 were treated chronically with D2, 14 with calcitriol. Data were extracted from medical records.

Main Outcome Measures

Serum creatinine and calcium, hospitalizations, and emergency department (ED) visits for hypercalcemia and hypocalcemia.

Results

D2 and calcitriol groups were similar in age (58.9 ± 16.7 vs 50.9 ± 22.6 years, P = 0.28), sex, and treatment duration (17.8 ± 14.2 vs 8.5 ± 4.4 years, P = 0.076). Hospitalization or ED visits for hypocalcemia occurred in none of the D2 group vs four of 14 in the calcitriol group (P = 0.03); three in the calcitriol group had multiple ED visits. There were no differences between D2 and calcitriol groups in hospitalizations or ED visits for hypercalcemia, serum creatinine or calcium, or kidney stones.

Conclusion

We found less morbidity from hypocalcemia in hypoparathyroid patients treated chronically with D2 compared with calcitriol and found no difference in renal function or morbidity from hypercalcemia. Treatment with D2 should be considered in patients with hypoparathyroidism, particularly in those who experience recurrent hypocalcemia.

Site-Specific Difference of Bone Geometry Indices in Hypoparathyroid Patients

BACKGROUND

Hypoparathyroid patients often have a higher bone mineral density (BMD) than the general population. However, an increase in BMD does not necessarily correlate with a solid bone microstructure. This study aimed to evaluate the bone microstructure of hypoparathyroid patients by using hip structure analysis (HSA).

METHODS

Ninety-five hypoparathyroid patients >20 years old were enrolled and 31 of them had eligible data for analyzing bone geometry parameters using HSA. And among the control data, we extracted sex-, age-, and body mass index-matched three control subjects to each patient. The BMD data were reviewed retrospectively and the bone geometry parameters of the patients were analyzed by HSA.

RESULTS

The mean Z-scores of hypoparathyroid patients at the lumbar spine, femoral neck, and total hip were above zero (0.63±1.17, 0.48±1.13, and 0.62±1.10, respectively). The differences in bone geometric parameters were site specific. At the femoral neck and intertrochanter, the cross-sectional area (CSA) and cortical thickness (C.th) were higher, whereas the buckling ratio (BR) was lower than in controls. However, those trends were opposite at the femoral shaft; that is, the CSA and C.th were low and the BR was high.

CONCLUSION

Our study shows the site-specific effects of hypoparathyroidism on the bone. Differences in bone components, marrow composition, or modeling based bone formation may explain these findings. However, further studies are warranted to investigate the mechanism, and its relation to fracture risk.

Bone imaging in hypoparathyroidism

Hypoparathyroidism (HypoPT) is an uncommon endocrine disorder characterized by chronic deficiency or absence of parathyroid hormone (PTH), which leads to a profound reduction in bone remodeling. Subjects with HypoPT typically have bone mineral densities (BMDs) by dual-energy X-ray absorptiometry (DXA) above average at all skeletal sites, with greatest scores observed at the lumbar spine. Trabecular bone score (TBS), an indirect measure of bone microarchitecture, also appears to be normal in HypoPT. By peripheral quantitative computed tomography (pQCT) of the radius, volumetric BMD at cancellous and cortical compartments, as well as cortical area and thickness, are greater in hypoparathyroid subjects than in controls. The use of high-resolution pQCT (HRpQCT) confirmed the increase in cortical volumetric BMD but demonstrated reduced cortical thickness, associated with lower cortical porosity in HypoPT. Trabeculae tend to be more numerous but thinner in hypoparathyroid subjects. It is not clear whether these structural and the dynamic skeletal abnormalities in HypoPT affect bone strength or fracture risk. Treatment of HypoPT with PTH leads to improvement in bone remodeling rate, variable changes in bone density, and a transient increase in estimated bone strength. The effect of PTH therapy on fracture risk remains unknown. This article reviews skeletal involvement and the effect of PTH treatment in patients with HypoPT, as assessed by DXA, TBS, QCT, and HRpQCT. Data on bone strength and fracture risk in HypoPT are also reviewed here.

Prolonged Pharmacokinetic and Pharmacodynamic Actions of a Pegylated Parathyroid Hormone (1-34) Peptide Fragment

Polyethylene glycol (PEG) addition can prolong the pharmacokinetic and pharmacodynamic actions of a bioactive peptide in vivo, in part by impeding rates of glomerular filtration. For parathyroid hormone (PTH) peptides, pegylation could help in exploring the actions of the hormone in the kidney; e.g., in dissecting the relative roles that filtered versus blood-borne PTH play in regulating phosphate transport. It could also lead to potential alternate forms of treatment for hypoparathyroidism. We thus synthesized the fluorescent pegylated PTH derivative [Lys¹³ (tetramethylrhodamine {TMR}), Cys³⁵ (PEG-20,000 Da)]PTH(1-35) (PEG-PTH^TMR ) and its non-pegylated counterpart [Lys¹³ (TMR), Cys³⁵ ]PTH(1-35) (PTH^TMR ) and assessed their properties in cells and in mice. In PTHR1-expressing HEK-293 cells, PEG-PTH^TMR and PTH^TMR exhibited similar potencies for inducing cAMP signaling, whereas when injected into mice, the pegylated analog persisted much longer in the circulation (>24 hours versus ∼ 1 hour) and induced markedly more prolonged calcemic and phosphaturic responses than did the non-pegylated control. Fluorescence microscopy analysis of kidney sections obtained from the injected mice revealed much less PEG-PTH^TMR than PTH^TMR on the luminal brush-border surfaces of renal proximal tubule cells (PTCs), on which PTH regulates phosphate transporter function, whereas immunostained phosphorylated PKA substrate, a marker of cAMP signaling, was increased to similar extents for the two ligands and for each, was localized to the basolateral portion of the PTCs. Pegylation of a bioactive PTH peptide thus led to prolonged pharmacokinetic/pharmacodynamic properties in vivo, as well as to new in vivo data that support a prominent role for PTH action at basolateral surfaces of renal proximal tubule cells. © 2016 American Society for Bone and Mineral Research.

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.