Zavatta, Guido

Abstract Background: Basal ganglia calcification (BGC) is a well-known complication of hypoparathyroidism. It is currently thought that increased serum phosphate or calcium x phosphate product may be major risk factors. However, the pathophysiology of BGC is still unclear, since the literature is largely based on limited case series or case reports. Methods: We identified a large cohort of patients with hypoparathyroidism diagnosed between 2000 and 2020 and evaluated those with head CT scans performed over this interval. Etiology and date of onset of hypoparathyroidism were determined by medical records review. All head CT scan images were reviewed to confirm radiology reports reporting BGC. We retrieved laboratory data within 10 years before the first head CT that showed incident BGC. Three age- and sex- matched controls with head CT scans were selected for each patient, and compared to the patients with hypoparathyroidism. Results: Of 1014 unique patients with a verified diagnosis of hypoparathyroidism, 142 had a head CT scan performed between 2000 and 2020. Head CT scans were performed for reasons unrelated to hypoparathyroidism in 96.5% of patients. In this cohort, 80.3% of patients (n=114) had post-surgical hypoparathyroidism. Age at which the first head CT in patients was done was 62±20.6 (range 11–97), and duration of hypoparathyroidism at the time of first head CT was 11.0±14.4 years (0–71). Prevalence of BGC in patients with hypoparathyroidism was 25.4% (n=36), as compared with 7.3% in the control group (31/426) (P<0.001). Patients and controls were similar in terms of cardiovascular risk factors (diabetes, hypertension, dyslipidemia, alcohol consumption, smoking status and BMI). In patients with non-surgical hypoparathyroidism (n=28), prevalence of BGC was 71.4% vs. 14.0% in the postsurgical cohort (OR 15.4; 95% CI 5.8–40, P<0.001). Compared to patients with hypoparathyroidism without BGC, those with BGC had lower time-weighted average serum calcium (8.4±0.8 vs. 8.8±0.8, P=0.002; normal range, 8.6–10.2 mg/dL), and lower time-weighted average calcium/phosphate ratio (Ca/P) (1.83±0.52 vs. 2.13±0.47, P=0.007). Conclusions: Basal ganglia calcification in hypoparathyroidism is associated with low serum calcium and low Ca/P ratio. This may allow increased bioavailability of phosphate in the extracellular space, leading to calcium phosphate crystal formation within the basal ganglia. Assessing Ca/P ratio may be useful to identify patients at risk for BGC. Prevalence of BGC is significantly higher in patients with non-surgical hypoparathyroidism.

Abstract Context Hypoparathyroidism is characterized by low serum calcium, increased serum phosphorus, and inappropriately low or decreased serum parathyroid hormone, which may be associated with soft tissue calcification in the basal ganglia of the brain. Objective To assess the prevalence and factors involved in the pathophysiology of basal ganglia calcification (BGC) in the brain in chronic hypoparathyroidism and to evaluate proposed pathophysiologic mechanisms. Design Case-control study with retrospective review of medical records over 20 years. Setting Single academic medical center. Patients 142 patients with chronic hypoparathyroidism and computed tomography (CT) head scans followed between January 1, 2000 and July 9, 2020, and 426 age- and sex-matched controls with CT head scans over the same interval. Interventions None. Main Outcome Measures Demographic, biochemical, and CT head imaging findings, with semiquantitative assessment of volumetric BGC. Results The study found that 25.4% of 142 patients followed for a median of 17 years after diagnosis of chronic hypoparathyroidism had BGC, which developed at a younger age than in controls. BGC was 5.1-fold more common in nonsurgical patients and less common in postsurgical patients. Low serum calcium and low calcium/phosphate ratio correlated with BGC. Neither serum phosphorus nor calcium × phosphate product predicted BGC. Lower serum calcium was associated with greater volume of BGC. The extent of BGC varied widely, with nonsurgical patients generally having a greater volume and distribution of calcification. Conclusions BGC is associated with low serum calcium and low serum calcium/phosphate ratio, which may be related to severity of the disease, its etiology, or duration of treatment.

The first adjunctive hormone therapy for chronic hypoparathyroidism, recombinant human parathyroid hormone (1–84) (rhPTH(1–84)) was approved by the FDA in January 2015. Since the approval of rhPTH(1–84), growing interest has developed in other agents to treat this disorder in both the scientific community and among pharmaceutical companies. For several reasons, conventional therapy with calcium and activated vitamin D supplementation, magnesium supplementation as needed, and occasionally thiazide-type diuretic therapy remains the mainstay of treatment, while endocrinologists and patients are constantly challenged by limitations of conventional treatment. Serum calcium fluctuations, increased urinary calcium, hyperphosphatemia, and a constellation of symptoms that limit mental and physical functioning are frequently associated with conventional therapy. Understanding how conventional treatment and hormone therapy work in terms of pharmacokinetics and pharmacodynamics is key to effectively managing chronic hypoparathyroidism. Multiple questions remain regarding the effectiveness of PTH adjunctive therapy in preventing or slowing the onset and progression of the classical complications of hypoparathyroidism, such as chronic kidney disease, calcium-containing kidney stones, cataracts, or basal ganglia calcification. Several studies point toward an improvement in the quality of life during replacement therapy. This review will discuss current clinical and research challenges posed by treatment of chronic hypoparathyroidism. Key points: Conventional therapy with calcium and activated forms of vitamin D are currently the mainstays of treatment for most patients with chronic hypoparathyroidism. Hormone therapy can be administered through FDA-approved once-daily rhPTH(1–84), or off-label multiple-daily injections of teriparatide. The former is the only FDA-approved drug, with safety and efficacy supported by a randomized placebo-controlled trial and open-label long-term extension trial data. Twice-daily teriparatide has been used in children safely for up to 10 years. New pharmacological options that replace the deficient hormone wi ll likely be available within the next few years.

ABSTRACT Normocalcemic primary hyperparathyroidism (NHPT) was first described over 10 years ago, but uncertainties still remain about its definition, prevalence, and rates of complications. As a result, consensus management guidelines for this condition have not yet been published. Several hypotheses have been proposed for the pathophysiology of NHPT, but it may be a heterogeneous disorder with multiple causes, rather than a single etiology that explains this biochemical phenotype. A common clinical concern is whether NHPT should be treated surgically when complications are already present at first recognition of the disorder, rather than following patients clinically over time. The literature on NHPT is based mostly on larger studies of population‐based cohorts and smaller studies from referral centers. Lack of rigorous diagnostic criteria and selection bias inherent in populations seen at tertiary referral centers may explain the heterogeneity of reported rates of bone and renal complications in relation to consistently mild laboratory alterations. Unresolved questions remain about the significance of NHPT when it is diagnosed biochemically without evident bone or kidney complications. Moreover, its natural history remains to be elucidated because a proportion of what is classified as NHPT may revert to normal spontaneously, thus revealing previously unrecognized secondary hyperparathyroidism. These issues indicate that caution should be used in recommending surgery for NHPT. This review will focus on recent issues regarding the pathophysiology, evaluation, and management of NHPT. © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.