Long-term follow-up of patients with hypoparathyroidism

CONTEXT

Despite tremendous interest in hypoparathyroidism, large cohort studies describing typical treatment patterns, laboratory parameters, and rates of complications are lacking.

OBJECTIVE

Our objective was to characterize the course of disease in a large cohort of hypoparathyroid patients.

DESIGN AND SETTING

We conducted a chart review of patients with permanent hypoparathyroidism identified via a clinical patient data registry. Patients were seen at a Boston tertiary-care hospital system between 1988 and 2009.

PATIENTS

We identified 120 patients. Diagnosis was confirmed by documented hypocalcemia with a simultaneous low or inappropriately normal PTH level for at least 1 yr. Mean age at the end of the observation period was 52 ± 19 (range 2-87) yr, and the cohort was 73% female.

MAIN OUTCOME MEASURE

We evaluated serum and urine laboratory results and renal and brain imaging.

RESULTS

We calculated time-weighted average serum calcium measurements for all patients. The time-weighted average for calcium was between 7.5 and 9.5 mg/dl for the majority (88%) of patients. Using linear interpolation, we estimated the proportion of time within the target calcium range for each patient with a median of 86% (interquartile range 67-98%). Of those with a 24-h urine collection for calcium (n = 53), 38% had at least one measurement over 300 mg/d. Of those with renal imaging (n = 54), 31% had renal calcifications, and 52% of those with head imaging (n = 31) had basal ganglia calcifications. Rates of chronic kidney disease stage 3 or higher were 2- to 17-fold greater than age-appropriate norms.

CONCLUSIONS

Hypoparathyroidism and its treatment carry a large burden of disease. Renal abnormalities are particularly common.

Association between activating mutations of calcium-sensing receptor and Bartter's syndrome

Bartter's syndrome is a heterogeneous disorder characterised by deficient renal reabsorption of sodium and chloride, and hypokalaemic metabolic alkalosis with hyper-reninaemia and hyperaldosteronaemia. Mutations in several ion transporters and channels have been associated with the pathogenesis of Bartter's syndrome. We describe two hypocalcaemic patients with deficient parathyroid hormone secretion who also showed characteristics of Bartter's syndrome. We found activating mutations of the gene for the calcium-sensing receptor (CASR) in both patients. Activation of this calcium-sensing receptor inhibits the activity of a renal outer-medullary potassium channel that is mutated in type 2 Bartter's syndrome. We therefore suggest that some activating mutations of CASR could provide new mechanisms for the development of Bartter's syndrome.

Nephrogenous cyclic adenosine monophosphate as a parathyroid function test

Nephrogenous cyclic AMP (NcAMP), total cyclic AMP excretion (UcAMP), and plasma immunoreactive parathyroid hormone (iPTH), determined with a multivalent antiserum, were prospectively measured in 55 control subjects, 57 patients with primary hyperparathyroidism (1 degrees HPT), and 10 patients with chronic hypoparathyroidism. In the group with 1 degrees HPT, NcAMP was elevated in 52 patients (91%), and similar elevations were noted in subgroups of 26 patients with mild (serum calcium </=10.7 mg/dl) or intermittent hypercalcemia, 19 patients with mild renal insufficiency (mean glomerular filtration rate, 64 ml/min), and 10 patients with moderate renal insufficiency (mean glomerular filtration rate, 43 ml/min). Plasma iPTH was increased in 41 patients (73%). The development of a parametric expression for UcAMP was found to be critically important in the clinical interpretation of results for total cAMP excretion. Because of renal impairment in a large number of patients, the absolute excretion rate of cAMP correlated poorly with the hyperparathyroid state. Expressed as a function of creatinine excretion, UcAMP was elevated in 81% of patients with 1 degrees HPT, but the nonparametric nature of the expression led to a number of interpretive difficulties. The expression of cAMP excretion as a function of glomerular filtration rate was developed on the basis of the unique features of cAMP clearance in man, and this expression, which provided elevated values in 51 (89%) of the patients with 1 degrees HPT, avoided entirely the inadequacies of alternative expressions. Results for NcAMP and UcAMP in nonazotemic and azotemic patients with hypoparathyroidism confirmed the validity of the measurements and the expressions employed.

Epidemiology and Diagnosis of Hypoparathyroidism

CONTEXT

Hypoparathyroidism is a disorder characterized by hypocalcemia due to insufficient secretion of PTH. Pseudohypoparathyroidism is a less common disorder due to target organ resistance to PTH. This report summarizes the results of the findings and recommendations of the Working Group on Epidemiology and Diagnosis of Hypoparathyroidism.

EVIDENCE ACQUISITION

Each contributing author reviewed the recent published literature regarding epidemiology and diagnosis of hypoparathyroidism using PubMed and other medical literature search engines.

EVIDENCE SYNTHESIS

The prevalence of hypoparathyroidism is an estimated 37 per 100 000 person-years in the United States and 22 per 100 000 person-years in Denmark. The incidence in Denmark is approximately 0.8 per 100 000 person-years. Estimates of prevalence and incidence of hypoparathyroidism are currently lacking in most other countries. Hypoparathyroidism increases the risk of renal insufficiency, kidney stones, posterior subcapsular cataracts, and intracerebral calcifications, but it does not appear to increase overall mortality, cardiovascular disease, fractures, or malignancy. The diagnosis depends upon accurate measurement of PTH by second- and third-generation assays. The most common etiology is postsurgical hypoparathyroidism, followed by autoimmune disorders and rarely genetic disorders. Even more rare are etiologies including parathyroid gland infiltration, external radiation treatment, and radioactive iodine therapy for thyroid disease. Differentiation between these different etiologies is aided by the clinical presentation, serum biochemistries, and in some cases, genetic testing.

CONCLUSIONS

Hypoparathyroidism is often associated with complications and comorbidities. It is important for endocrinologists and other physicians who care for these patients to be aware of recent advances in the epidemiology, diagnosis, and genetics of this disorder.

Long-term treatment of hypoparathyroidism: a randomized controlled study comparing parathyroid hormone-(1-34) versus calcitriol and calcium

Hypoparathyroidism is one of the few remaining hormonal insufficiency states for which replacement therapy is unavailable. Previous short-term controlled trials have shown PTH to be a safe and effective treatment of hypoparathyroidism. In this randomized, parallel group, open-label trial, we compared synthetic human PTH-(1-34) (PTH) with conventional therapy, calcitriol and calcium, over a 3-yr period. Twenty-seven patients with confirmed hypoparathyroidism, aged 18-70 yr, were randomized to either twice daily sc PTH or oral calcitriol and calcium. The primary end points were calcium levels in serum and urine. Secondary end points were creatinine clearance, markers of bone turnover, and bone mineral density. Throughout the 3-yr study period, serum calcium levels were similar in both treatment groups within or just below the normal range. Mean urinary calcium excretion was within the normal range from 1-3 yr in PTH-treated patients, but remained above normal in the calcitriol group. Bone mineral content and bone mineral density showed no significant between-group differences over the 3-yr study period. We conclude that treatment with twice daily sc PTH provides a safe and effective alternative to calcitriol therapy and is able to maintain normal serum calcium levels without hypercalciuria for at least 3 yr in patients with hypoparathyroidism.

Magnesium deficiency and cardiac disorders

Magnesium deficiency can occur in congestive heart failure, after diuresis with furoxemide, ethacrynic acid and mercurials, and with digitalis intoxication, diabetic acidosis, acute and chronic alcoholism, delerium tremens, cirrhosis, malabsorption syndromes, protracted postoperative cases, open heart surgery, the diuretic phase of acute tubular necrosis, and with hypoparathyroidism, primary aldosteronism, juxta-glomerular hyperplasia and pancreatitis. Two cases of serious ventricular arrhythmias associated with magnesium depletion are described. Clinical manifestations are vague but center around neurologic symptoms such as weakness, tremors, stupor, coma, nausea, vomiting and anorexia. Serious cardiac arrhythmias also occur with magnesium depletion. Magnesium appears to be very useful in hypomagnesemic or digitalis-toxic tachyarrhythmias. Magnesium may also be valuable in normomagnesemic tachyarrhythmias. Ten to fifteen milliliters of a 20 percent magnesium sulfate solution, given intravenously over 1 minute, followed by a slow 4 to 6 hour infusion of 500 ml of 2 per cent magnesium sulfate in 5 per cent dextrose in water is recommended. Recurrence of arrhythmias is common and a second infusion of magnesium sulfate may be necessary. Hypermagnesemia occurs frequently in renal insufficiency, and magnesium therapy may then be contraindicated. Serum levels above 5.5 meq/liter should be avoided. Loss of deep tendon reflexes and a decrease in respiratory rate can be used as guides to magnesium therapy. A plea is made for frequent analysis of serum magnesium so that more knowledge can be gained regarding this important biologic element in cardiovascular disorders.

Low parathyroid hormone levels after thyroid surgery: a feasible predictor of hypocalcemia

BACKGROUND

Selecting patients with a low risk of hypocalcemia is mandatory if patients are to be discharged on the first day after bilateral thyroidectomy. This study investigated the predictive value of intraoperative parathyroid hormone (PTH).

METHODS

Thirty-eight patients underwent total or near-total thyroidectomy. Patients with or without biochemical and symptomatic hypocalcemia were compared regarding intraoperative PTH levels and previously suggested risk factors. The accuracy of intraoperative PTH to predict patients at risk for postoperative hypocalcemia was compared with a calcium concentration of less than 2.00 mmol/L (8.0 mg/dL) on the first postoperative day.

RESULTS

PTH levels after resection of the second lobe, age, and number of parathyroid glands identified intraoperatively were independently associated with the reduction in serum calcium concentration measured at nadir on the first or second postoperative day. PTH levels after resection of the second lobe were lower among patients who developed biochemical (P <.001) and symptomatic hypocalcemia (P <.01) compared with those who did not. Low levels of intraoperative PTH identified the 3 patients who required intravenous calcium during the first 24 postoperative hours. An intraoperative PTH level below reference range and a calcium concentration of less than 2.00 mmol/L measured 1 day postoperatively both predicted biochemical hypocalcemia with a similar sensitivity (90% vs 90%) and specificity (75% vs 82%). Intraoperative PTH was slightly better than a serum calcium concentration of less than 2.00 mmol/L on postoperative day 1 to predict symptomatic hypocalcemia, with a sensitivity of 71% vs 52% and a specificity of 81% vs 76%, respectively.

CONCLUSIONS

Parathyroid gland insufficiency is the main determinant of transient hypocalcemia after bilateral thyroid surgery. Low intraoperative PTH levels during thyroid surgery are therefore a feasible predictor of postoperative hypocalcemia.

Multicentre study on prevalence of endocrine complications in thalassaemia major. Italian Working Group on Endocrine Complications in Non-endocrine Diseases

OBJECTIVE

Thalassaemia major is a common and serious medical problem, worldwide. However, there are few data concerning the various endocrine disorders which occur in this condition. We have surveyed 25 Italian centres in order to establish the prevalences and times of onset of endocrine disorders in patients with beta-thalassaemia major. PROJECT AND PATIENTS: A questionnaire specifically designed to investigate the prevalences of endocrinopathies was sent to 25 paediatric and haematology departments. The following data were recorded in the questionnaire: sex, age, height and weight, pubertal status according to Tanner's classification, history of secondary amenorrhoea, type of endocrinopathy and hormone levels at diagnosis, associated complications, serum ferritin level, liver enzymes (ALT) and compliance with treatment.

RESULTS

An analysis of data from 1861 patients showed that failure of puberty was the major clinical endocrine problem and was present in 51% of boys and 47% of girls, all over the age of 15 years. Secondary amenorrhoea was recorded in 23% of patients (mean age 18.3 years), primary hypothyroidism in 6.2% (mean age 15.8 years), insulin dependent diabetes mellitus in 4.9% (mean age 18.1 years) and hypoparathyroidism in 3.6% of the patients (mean age 18.7 years). At present, the majority are in the second or third decades of life. The prevalences of hypothyroidism, insulin dependent diabetes mellitus and hypoparathyroidism differed in the various centres, whereas the frequency of pubertal disorders was very similar.

CONCLUSIONS

Our study has demonstrated several points. Endocrine evaluation in thalassaemic patients must be carried out regularly, especially in those patients over the age of 10 years with iron overload and poor compliance with chelation therapy. The prevalences of some complications, such as insulin dependent diabetes and hypothyroidism, were lower than previously recorded. Hence, it is to be hoped endocrine complications will be less common in the future, for patients who have started chelation therapy during the first years of life. Because of the improved survival of thalassaemic patients with insulin dependent diabetes, and the high incidence of multiple endocrine complications, it is important to carry out careful follow-up studies for the early detection of any other associated complications to facilitate correct treatment.

Activating antibodies to the calcium-sensing receptor in two patients with autoimmune hypoparathyroidism

Autoimmune hypoparathyroidism is thought to result from immune-mediated destruction of the parathyroid glands. We encountered two patients with hypoparathyroidism and other autoimmune conditions (Graves' disease and Addison's disease, respectively) in whom autoimmune destruction of the parathyroid glands had not taken place. In the first, a histologically normal parathyroid gland was observed at the time of subtotal thyroidectomy; and in the second, the hypoparathyroidism remitted spontaneously. Both patients had antibodies that reacted with the cell surface of bovine parathyroid cells and human embryonic kidney (HEK293) cells transfected with the extracellular calcium-sensing receptor (CaR) but not with nontransfected HEK293 cells. The antibodies also reacted with the same bands on Western analysis of extracts of bovine parathyroid tissue and CaR-transfected HEK293 cells that were identified by an authentic, polyclonal, anti-CaR antiserum and reacted with several peptides with sequences from the CaR's extracellular domain. These anti-CaR antibodies activated the receptor based on their ability to increase inositol phosphate accumulation, activate MAPK, and inhibit PTH secretion. These results, therefore, demonstrate that patients with the biochemical findings of primary hypoparathyroidism can harbor activating antibodies to the CaR, which, in the two cases studied here, did not produce irreversible destruction of the parathyroid glands.

Calcification of the basal ganglia: computerized tomography and clinical correlation

During a 1-year period, 4219 consecutive computerized tomograms (CT) were reviewed for basal ganglia calcification; 14 patients with such calcification were identified. Calcifications on CT scan were bilateral in 12 of these cases and unilateral in 2. All bilateral calcifications were symmetric. The globus pallidus was the site of calcification in 13 of the 14 patients. Bilateral dentate nucleus calcification was seen in one patient. Skull radiograms were normal in all but one. Patients had diverse symptoms that were often explained by other findings, suggesting that calcifications may be coincidental and that basal ganglia calcification may not be a nosologic entity. Disturbances of calcium metabolism were not found in these patients, minimizing the pathophysiologic significance of altered calcium metabolism and the need for extensive endocrinologic evaluation. The finding of basal ganglia calcification alone does not justify invasive diagnostic procedures. Extrapyramidal signs may be associated with basal ganglia calcification; parkinsonism associated with basal ganglia calcification differs from idiopathic parkinsonism in being resistant to levodopa therapy.

Etiologic factors in hypocalcemia secondary to operations for carcinoma of the pharynx and larynx

Hypocalcemia, although a relatively uncommon sequela of operations for carcinoma of the larynx and pharynx, often presents as an acute medical emergency. In its chronic form, hypocalcemia may be a difficult disorder to control. Understanding the etiologic basis of hypocalcemia secondary to operations for carcinoma of the head and neck requires knowledge of the pathophysiology of the preoperative and postoperative factors affecting calcium homeostasis. These factors include thyroidectomy, hypoparathyroidism, hypomagnesemia, anticonvulsant therapy, estrogen replacement therapy, oral contraceptives, blood transfusions, hyperventilation alkalosis, hypoalbuminemia, corticosteroid therapy, depression, emotional stress and diet. Often the onset of symptoms and signs of hypocalcemia occurs within 24 to 48 hours after the operation. The symptoms may include mental depression, headache, tingling of the hands and perioral region and abdominal pain. Unrecognized chronic hypocalcemia may lead to the development of cataracts, convulsions and psychosis.

Activating mutations of the calcium-sensing receptor: management of hypocalcemia

Activating mutations of the calcium-sensing receptor (CaR) can cause isolated hypoparathyroidism. Treatment of hypocalcemia in these patients remains to be optimized, because the use of 1-hydroxylated vitamin D3 derivatives can cause hypercalciuria and nephrocalcinosis. We identified activating CaR mutations in 8 (42%) of 19 unrelated probands with isolated hypoparathyroidism. The severity of hypocalcemic symptoms at diagnosis was independent of age, mutation type, or mode of inheritance but was related to the degree of hypocalcemia; serum Ca was 1.97 +/- 0.08, 1.82 +/- 0.14, and 1.54 +/- 0.22 mmol/liter, respectively, in asymptomatic (n = 7), mildly symptomatic (n = 8), and severely symptomatic patients (n = 6). Hypocalcemia segregated with the CaR mutation, but no phenotype-genotype relationships were identified. Fourteen patients received regular 1-hydroxylated vitamin D3 treatment (mean duration, 7.2 +/- 4.9 yr). Nine had hypercalciuric episodes, which were associated with nephrocalcinosis in eight cases. Serum Ca during treatment predicted hypercalciuria and nephrocalcinosis poorly, because either or both of the latter could develop in hypocalcemic patients. Thus, mutational analysis of the CaR gene should be considered early in the work-up of isolated hypoparathyroidism. Treatment options should be weighed carefully in patients with serum Ca below 1.95 mmol/liter. The risk of nephrocalcinosis during treatment can be minimized by carefully monitoring urinary Ca excretion.

Evidence for defective immunoregulation in the syndrome of familial candidiasis endocrinopathy

We studied three children with candidiasis endocrinopathy syndrome, together with their parents and five siblings, to explore the possibility that defective immunoregulation allows autoimmune phenomena to be involved in the pathogenesis of this syndrome. Inheritance of the syndrome appeared to be autosomal recessive. Immunologic abnormalities in this family included hypergammaglobulinemia, selective IgA deficiency, anergy, autoimmune endocrinopathies and active chronic hepatitis. Defective suppressor T-cell function was noted in the two surviving children with clinically apparent disease and in a clinically normal sibling. Analysis of the immunologic abnormalities in the family suggests that defective immunoregulation rather than disordered effector mechanisms may explain the large number of immunologic defects noted. These defects, in turn, may result in the clinical manifestation of the syndrome.

Recovery of parathyroid hormone secretion after parathyroid adenomectomy

Using a sensitive two-site immunoradiometric assay which detects only intact human PTH-(1-84), we studied the kinetics of PTH secretion in 19 patients undergoing unilateral neck exploration and removal of a parathyroid adenoma. Preoperative serum PTH values averaged 116 ng/L (normal, 12-65 ng/L). In 8 patients in whom intraoperative sampling was performed, clearance of PTH-(1-84) was rapid, with virtual disappearance of PTH by 120 min after clamping the vascular pedicle to the adenoma. Analysis of the rate of disappearance of PTH-(1-84) indicated an exponential decay with a half-life of 21 min. Thirteen of 19 patients had serum PTH values less than 1 ng/L within 8 h after parathyroidectomy. Recovery of PTH secretion from the suppressed nonsurgically manipulated parathyroid tissue occurred during the nadir of postoperative hypocalcemia. Serum PTH was greater than 10 ng/L in 16 of 19 patients 30 h after removal of the PTH adenoma. Therefore, the functional recovery of atrophic parathyroid tissue is more rapid than that of other endocrine tissues studied to date.

Prevalences of CT-detected calcification in the basal ganglia in idiopathic hypoparathyroidism and pseudohypoparathyroidism

Sixteen patients with idiopathic hypoparathyroidism (IHP) and eight patients with pseudohypoparathyroidism (PHP) were examined by CT scan of the brain. Calcification in the basal ganglia was observed in 11 patients with IHP (69%) and in all eight patients with PHP. Of the 19 patients with basal ganglia calcification, nine had calcification in the cerebral cortex (47%), and four had calcification in the cerebellum (21%). Observation of basal ganglia calcification on CT gave rise to suspicion of IHP or PHP in three patients (12%). The remaining patients were examined at varying time after diagnosis. Since arrest in growth of calcification after institution of treatment has never been proven, the reported prevalences of calcification may not be valid to the situation at the time of diagnosis.

HDR syndrome (hypoparathyroidism, sensorineural deafness, renal dysplasia) associated with del(10)(p13)

A combination of hypoparathyroidism, sensorineural deafness, and renal dysplasia has been considered to be a new syndrome inherited in an autosomal dominant fashion; we name the condition "HDR syndrome." We describe a Japanese girl who has HDR syndrome associated with de novo del(10)(p13). The chromosome deletion suggests that the putative gene(s) responsible for HDR syndrome is located at a 10pter-->p13 region.

Bilateral basal ganglia calcifications visualised on CT scan

Thirty-eight cases of basal ganglia calcification imaged on computed axial tomography were reviewed. Most cases were felt to represent senescent calcification. The possibility of a vascular aetiology in this group is discussed. A less common group of patients was identified with calcification secondary to abnormalities in calcium metabolism or radiation therapy. Three cases of basal ganglia calcifications were detected in juvenile epileptic patients receiving chronic anticonvulsants. These cases may be related to abnormalities in calcium metabolism and alkaline phosphatase activity. Clinical evidence of basal ganglia abnormality was generally absent demonstrating the preservation of neuronal pathways in most cases.