[Fluoride toxicity]

Many years have passed since domestic water fluoridation was adopted to reduce the incidence of caries in developed countries; however, since there is an additional dose of fluorides ingested with foods and drinks prepared with such waters, the problem has emerged of possible adverse effects on health associated to them, so that in some countries fluorine integrator selling is allowed only with preventive medical prescription. Owing to the affinity for calcifited tissues, fluorine has a powerful effect on bone cellular order (mediated by growth factors' upregulation system IGF-2, TGF-beta, PDGF, bFGF, EGF, BMP-2 and PTH), on function and length, since it can provoke chronic joints-pain, ligaments-calcification, osteosclerosis. Moreover, sodium-fluoride may cause adverse effects on testicular activity (connected to oxidative-stress depending on increased activity of peroxidases and catalases) due to inhibition of 2 androgenesis-regulator enzymes DELTA(5)b-HSD and 17beta-HSD. Furthermore, insoluble gut formed calcium-fluoride may be responsible for hypocalcemia inducing a secondary hyperparathyroidism with bone matrix resorption, osteoporosis, osteomalacia and, perhaps, lowered level of phosphorus. At encephalic level, then, high doses of fluorine cause the onset of neurological symptoms and of a decreased spontaneous motor activity due to a reduction in the number of nicotinic acetylcholine receptors. Nevertheless, epidemiological studies about fluoride toxicity have established that such oligoelement may be safely used at odontoiatric dosages.

Pathophysiology of bone loss in patients receiving anticonvulsant therapy

Many studies have shown that patients taking antiepileptic drugs (AEDs) are at increased risk for metabolic bone disease and low bone mineral density. Although early reports of bone disease in patients with epilepsy often involved institutionalized patients, who may be at risk because of lack of physical activity, reduced sunlight exposure, and poor nutrition, low bone density has also been reported in well-nourished, ambulatory outpatients with epilepsy. Traditionally, attention to the problem of AED-induced bone loss has been focused on those drugs that induce the hepatic cytochrome P450 enzyme system, thereby increasing the metabolism of vitamin D. However, the mechanisms of AED-induced bone loss appear to be multiple, and all types of AEDs are potentially implicated. Besides hepatic enzyme induction, mechanisms may include direct effects of AEDs on bone cells, resistance to parathyroid hormone, inhibition of calcitonin secretion, and impaired calcium absorption. An understanding of bone biology and the pathophysiology of bone loss can aid in the identification and monitoring of patients at risk and in the planning of appropriate prophylactic and therapeutic measures, by which most of the morbidity associated with AED-induced bone loss can be prevented.

Prolonged high-dose phosphate treatment: a risk factor for tertiary hyperparathyroidism in X-linked hypophosphatemic rickets

OBJECTIVE

X-linked hypophosphatemic rickets is characterized by renal phosphate wasting, hypophosphatemia and defective bone mineralization. Treatment with oral phosphate (Pi) and calcitriol improves skeletal changes but associates with secondary hyperparathyroidism and nephrocalcinosis. Tertiary hyperparathyroidism is a rare complication of the treatment. The aim of the present study was to identify treatment-related factors that might be associated with the transition of secondary hyperparathyroidism to tertiary hyperparathyroidism in patients with X-linked hypophosphatemic rickets.

DESIGN

Thirteen patients with X-linked hypophosphatemic rickets and secondary or tertiary hyperparathyroidism were included in the study. Their hospital records were reviewed and compared for onset, duration and dosage of treatment, and for age of diagnosis and degree of secondary hyperparathyroidism.

RESULTS

Two patients developed tertiary hyperparathyroidism and 11 patients secondary hyperparathyroidism during the treatment. Patients with tertiary hyperparathyroidism had, on average, earlier onset and longer duration of treatment, higher dose of Pi and longer duration of treatment with very high Pi doses (> 100 mg/kg/day) compared to the 11 patients with secondary hyperparathyroidism. However, variation of all parameters was great with considerable overlap. Very high S-PTH levels > or = 42 pmol/l were observed in those who later developed tertiary hyperparathyroidism.

CONCLUSIONS

Prolonged very high dose oral Pi treatment is a major risk factor for the development of tertiary hyperparathyroidism in X-linked hypophosphatemic rickets.

Hypertension in hypophosphatemic rickets--role of secondary hyperparathyroidism

Hypertension has been anecdotally reported in children with familial hypophosphatemic rickets (XLH). To better identify and characterize the clinical and laboratory features of hypertensive XLH children, we reviewed the medical records of 41 XLH children, all treated with phosphate and vitamin D analogues. Eight children, who were originally normotensive, developed hypertension during the 2nd decade of life. At diagnosis of hypertension all had persistent secondary/tertiary hyperparathyroidism (HPTD), defined as high serum parathyroid hormone (PTH) for 12 months or longer. Seven had nephrocalcinosis (NC). Analysis of data showed that of 11 children with HPTD, 8 developed hypertension compared with 0 among 30 without HPTD (P<0.001). Of 40 children studied, 18 had NC that was significantly associated with both HPTD (P<0.01) and hypertension (P<0.025). At diagnosis of hypertension, serum calcium was elevated in 2. Plasma renin activity was high in 3 of 4 patients in whom it was measured. Doppler ultrasonography or renal scan was normal in the 5 children studied. Early echocardiography showed left ventricular hypertrophy in only 2 of 5 children studied. In 3 patients who underwent parathyroidectomy, hypertension persisted and 1 progressed to renal failure. Serum creatinine remained normal in all others. Successful treatment of hypertension consisted of beta-adrenergic blockers, angiotensin converting enzyme inhibitors, and Ca channel blockers as monotherapy or in combination. We conclude that hypertension in treated XLH children is closely associated with HPTD. Emphasis should therefore be placed on prevention of the development of HPTD as a complication of XLH treatment, and close monitoring for hypertension in those who do develop HPTD.

[Lithium induced dysfunction of the parathyroid hormone]

The prevalence of hyperparathyroidism (HPT) in patients treated with lithium is higher than that in controls. Lithium seems to affect calcium metabolism, by acting directly parathyroid hormone cells, and distal tubuli in the kidneys. Because hypercalcaemic HPT can cause psychiatric symptoms mistakenly attributed to the lithium treatment, ionised calcium should be a standard control.

[Hyperparathyroidism secondary to anticonvulsant treatment]

Treatment with some anticonvulsants is known to lead to liver enzyme induction. Two cases suggest that this interaction is also the mechanism behind anticonvulsant osteomalacia, which is characterised by hypocalcaemia, elevated alkaline phosphatase, and low 25(OH) cholecalciferol.

Intravenous versus oral vitamin d therapy in dialysis patients: what is the question?

The debate regarding the administration of vitamin D (parenteral versus pulse oral) in dialysis patients has centered on the efficacy of parathyroid hormone (PTH) suppression while ignoring other questions related to complications and compliance. Past studies looking at efficacy showed no differences during short-term treatment, although the small number of patients studied reduces the significance of these findings. Long-term studies with larger populations have shown that parenteral calcitriol is more effective than pulse oral calcitriol in suppressing PTH. When considering the questions of complications and compliance the current literature demonstrates that parenteral vitamin D therapy is associated with fewer episodes of hypercalcemia and hyperphosphatemia and that patients receiving pulse oral calcitriol require more phosphate binders. Because of the documented high noncompliance rate with oral medications in the dialysis population, parenterally administered vitamin D is expected to more completely suppress PTH long term and result in fewer parathyroidectomies. Based on these considerations it is suggested that parenteral vitamin D analogs are superior to pulse oral calcitriol for the long-term control of hyperparathyroidism in dialysis patients.

[Lithium treatment and hyperparathyroidism]

BACKGROUND

Lithium treatment, which is extensively used in bipolar affective disorders, may give rise to hypercalcaemia and sometimes to irreversible hyperparathyroidism.

MATERIAL AND METHODS

We present a patient who developed hyperparathyroidism following long-term treatment with lithium.

RESULTS

After 15 years on lithium the patient was diagnosed with hypercalcaemia; at the same time the patient stopped her lithium medication. Two years later she developed depression with psychotic symptoms and was given electroconvulsive treatment. Measurements of serum calcium and parathormon showed that she had developed hyperparathyroidism. Neck exploration was performed, and two parathyroid adenomas (weight 650 mg and 880 mg), which had been detected by scintigraphy, were removed. Lithium treatment was restarted. One year later she was normocalcaemic and her mood was normal.

INTERPRETATION

In lithium-induced hyperparamyroidism, lithium should be replaced with other mood stabilizers, preferably an antiepilepticum. If cessation of lithium therapy does not lead to normocalcaemia, parathyroidectomy is indicated.

Secondary hyperparathyroidism exacerbation: a rare side-effect of interferon-alpha?

Recombinant human interferon alpha (alpha IFN) is the only treatment with proven benefit for chronic hepatitis C virus (HCV) infection. Nevertheless its use in some susceptible individuals has led to the development or aggravation of different autoimmune conditions. We report the case of a 20 year old woman on peritoneal dialysis with chronic lobular hepatitis secondary to HCV infection who developed de novo psoriasis 9 months after starting treatment with alpha-IFN. In addition to psoriasis, alpha-IFN prescription was also concurrent with an unexpected and refractory secondary hyperparathyroidism exacerbation initially characterized by a marked reduction of serum calcium levels and a consequential increase of PTH. Both complications disappeared after drug withdrawal. The clinical sequence makes an alpha-IFN-induced autoimmune side effect the most plausible hypothesis. The case is discussed and some possible etiopathogenic factors are briefly reviewed.

Intact parathyroid hormone levels are not elevated in glucocorticoid-treated subjects

To assess whether chronic glucocorticoid therapy results in a compensatory increase in parathyroid hormone (PTH), we measured intact PTH levels and other indices of mineral metabolism in 13 postmenopausal glucocorticoid-treated women and 16 normal age-matched controls. The glucocorticoid-treated women received a mean prednisone dose of 15.8 +/- 3.1 mg/day for 12.9 +/- 3.1 years. A linear regression analysis between intact PTH levels and a wide range of prednisone doses in these 13 glucocorticoid-treated women and 26 additional male and female subjects receiving chronic glucocorticoid therapy for a variety of rheumatic and pulmonary disorders (n = 39) was also performed. Intact PTH levels using the sensitive immunoradiometric assay (IRMA, Nichols Institute, San Juan Capistrano, CA) were comparable in the glucocorticoid-treated and normal control women (35.3 +/- 4.4 vs 31.3 +/- 3.2 ng/l, respectively) as wee the total calcium concentrations (9.67 +/- 0.12 vs 9.52 +/- 0.11 mg/dl). In the glucocorticoid-treated women, the 25-hydroxyvitamin D levels, measured by competitive protein assay were similar to those of the control subjects (29.2 +/- 2.8 vs 29.1 +/- 2.3 mg/ml), and no patient was treated with vitamin D in excess of 400 IU daily. In the combined 39 male and female patients, there were also no significant regression relationships between daily prednisone dose and intact PTH levels. Thus, secondary hyperparathyroidism does not accompany chronic oral glucocorticoid therapy in women on low to moderate doses of oral glucocorticoids. The lack of an elevation in intact PTH levels in the presence of chronic glucocorticoid therapy may represent an increased sensitivity of bone to PTH, or an alteration in the relationship between calcium and PTH, or both.

Biochemical hyperparathyroidism and bone mineral status in patients treated long-term with lithium

Lithium is known to interfere with normal calcium homeostasis, but the long-term effects and possible clinical significance are uncertain. Thus, we measured indices of parathyroid function including intact parathyroid hormone (PTH) and ionized and total calcium levels in 26 patients treated for manic-depressive psychosis with lithium for 10 years or longer (mean +/- SD duration, 15 +/- 6 years). Increased ionized calcium levels were found in 11 patients and increased PTH concentrations in five patients. Altogether, 54% of the patients (14 of 26) had ionized calcium and/or PTH levels above the laboratory reference range. The PTH/ionized calcium relationship of the lithium-treated patients was compared with that of a group of normal subjects (n = 23) and with those of three different groups of patients with abnormal parathyroid function (chronic hypoparathyroidism, n = 21; primary hyperparathyroidism [HPT], n = 50; and tertiary HPT, n = 21). Lithium-treated patients had significantly higher ionized calcium levels (P < .0001) but not significantly higher PTH concentrations (P = .08) than the normal subjects. In comparison to the normal controls, lithium-treated patients had a right-sided shift in their PTH/ionized calcium relationship that was in the same direction but less prominent than in primary or tertiary HPT. Dual-energy x-ray absorptiometry disclosed similar bone mineral densities (BMDs) of lithium-treated patients and age-, sex-, and body mass-matched normal controls in the whole body, lumbar spine, and femoral neck (Z scores: +1.20, +1.22, and +1.02, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Lithium-induced alterations in parathyroid cell function: insight into the pathogenesis of lithium-associated hyperparathyroidism

BACKGROUND

Reduced parathyroid sensitivity to changes in calcium (Ca2+) has been observed in patients treated with lithium (Li+). In order to investigate this desensitization phenomenon, the effect of Li+ on cytosolic calcium (Cai2+) regulation was examined.

METHODS

Transmembrane signal transduction and Ca2+ sequestration were investigated in bovine parathyroid cells by measuring changes in [Cai2+] in response to 5 mmol/L magnesium (Mg2+), 0.5 to 2.5 mmol/L Ca2+, 25 mumol/L adenosine triphosphate (ATP), and 1 mumol/L ionomycin in cells pretreated with 1 to 10 mmol/L lithium chloride (LiCl) and control cells. Measurement of Cai2+ was made using fura-2.

RESULTS

Increases in [Cai2+] in response to Ca2+ and Mg2+ were blunted following overnight culture with as low as 1 mmol/L LiCl. In normocalcemic medium, 1 mmol/L Ca2+ produced an 81% increase in [Cai2+] in control cells compared with a 58% increase in cells pretreated with LiCl (P < 0.01), whereas in hypocalcemic medium, increases in [Cai2+] were similar in lithium-treated and control cells (78% versus 82%, P > 0.1). The ATP produced increases in [Cai2+] from 225 +/- 9 nmol/L to 366 +/- 10 nmol/L in control cells, compared with 221 +/- 7 nmol/L to 308 +/- 10 nmol/L in cells pretreated with 5 mmol/L LiCl (P < 0.01). Ionomycin-induced increases in [Cai2+] were unaffected by Li+.

CONCLUSIONS

We concluded that the in vitro desensitizing effects of Li+ occur at therapeutic concentrations, but only in the presence of Ca2+ in concentrations that induce transmembrane signaling; and that Li+ blunts increases in [Cai2+] related to cation and ATP-induced transmembrane signal transduction without affecting ionomycin-releasable Ca2+ stores.

Calcium mass balance and behavior of intact immunoreactive parathyroid hormone in acetate-free biofiltration: acute and one-year evaluation

The present study evaluated calcium mass balance (MB) during acetate-free biofiltration (AFB) with a dialysate calcium concentration of 2 mmol/l and different ultrafiltration rates (UF; 42.5 ml/min in schedule 1 and 48.5 ml/min in schedule 3), and with a calcium concentration of 1.75 mmol/l but an UF of 43 ml/min (schedule 2). We also examined the effects of these schedules on the behavior of intact parathyroid hormone (I-PTH). AFB according to schedule 1 and 3 achieve a positive calcium MB (8.49 +/- 1.56 and 5.59 +/- 1.06 mmol, respectively), while in schedule 2 calcium MB merely balanced (0.07 +/- 2.29 mmol/l). A significant acute intradialytic I-PTH decrease was observed with all schedules; after 1 month, however, predialytic PTH values were unchanged in schedules 1 and 3, but worsening was noted in schedule 2. Subsequently, AFB was performed for 12 months employing a dialytic schedule (No. 1) involving a positive calcium balance. A year later I-PTH was significantly lower, thus proving that AFB may play an additional part in controlling secondary hyperparathyroidism.

Single-dose intravenous pamidronate is effective alternative therapy for Paget's disease refractory to calcitonin

We have conducted an open, prospective study to investigate the efficacy of a single 60 mg infusion of pamidronate as alternative therapy in 15 subjects with severe Paget's bone disease refractory to calcitonin. Disease activity was assessed with a visual-analogue score of symptom severity, plasma alkaline phosphatase and quantitative estimation of 99mTc-methylene biphosphonate uptake on bone scan. All indices of disease activity fell after pamidronate, reaching a nadir at 3 months. Although disease activity increased thereafter, only 3 subjects required retreatment within 12 months. Plasma calcium fell after 3 days and remained below baseline levels for 6 months associated with evidence of secondary hyperparathyroidism. Pamidronate was well tolerated; femoral neck fractures occurred in 2 subjects with severe local Paget's disease but were unlikely to be due to the drug. We conclude that pamidronate is an effective and promising alternative for treatment of patients with severe Paget's disease no longer adequately controlled by calcitonin. Calcium supplementation may be prudent to prevent secondary hyperparathyroidism associated with the use of this agent.

[Effect of fluoride on the skeletal system]

The chronic fluoride intoxication in man and animal may cause so different diseases of the bones as osteosclerosis, osteomalacia, secondary hyperparathyroidism and osteoporosis--partly in combination. On the basis of own examinations and of literature an own theory is developed which tries to explain these 4 contrary findings on the bone. According to this theory the fluor dosage, the calcium and vitamin D deficiency, differences of the species, duration of the fluoride supply and an individual sensitiveness to fluoride play an important role. Fluor has an effect on the 3 constituents of bones: osteoblasts, osteoclasts and the bone material.

Bone ultrastructure and x-ray microanalysis of aluminum-intoxicated hemodialyzed patients

In hemodialyzed patients aluminum (Al) intoxication may induce osteomalacic lesions which are mainly observed when plasma immunoreactive parathyroid hormone (iPTH) concentrations are low, and osteitis fibrosa absent. In this study, the bone tissue of eight hemodialyzed patients with elevated plasma and bone Al concentrations was examined by histomorphometry, electron microscopy, and x-ray microanalysis. Five patients (group 1) had osteomalacia and minimal osteitis fibrosa, three patients (group 2) had severe osteitis fibrosa. In group 1, Al was concentrated at the mineralizing front, in hexagonal structures measuring 200 to 1,000 A which also contained phosphorus, but not calcium. Hydroxyapatite needles had a normal aspect. Osteoblasts appeared inactive. In group 2, Al was also present at the mineralizing layer of osteoid, but, in these cases, in small clusters next to abnormal calcium deposits. Osteoblasts appeared very active. Their mitochondria contained calcium and phosphorus granules, or amorphous material, measuring 1,500 to 2,000 A, emitting x-rays characteristic for Al and phosphorus. These results suggest that secondary hyperparathyroidism, by stimulating the cellular activity, may increase the uptake and release of Al by the osteoblasts. The presence of Al within the mitochondria of these cells may be one of the factors inducing the mineralization defect.

Secondary hyperparathyroidism and bone disease in infants receiving long-term furosemide therapy

Four preterm infants receiving long-term furosemide therapy were examined for hypercalciuria, hyperparathyroidism, renal calcification, and bone demineralization. All four infants had increased urinary calcium excretion. Three infants had high serum concentrations of parathyroid hormone, and in these three infants, bone mineral content was below the mean of "osteopenic" preterm infants of comparable gestational and postnatal age. In two of these infants, there was ultrasound evidence of renal calcification. In one infant, autopsy disclosed bone changes of hyperparathyroidism, gallstones, and calcification in the heart and kidney.

Importance of increased urinary calcium excretion in the development of secondary hyperparathyroidism of patients under glucocorticoid therapy

Parathyroid function and calcium metabolism were studied in 44 patients under glucocorticoid therapy (steroid group) and in 25 control subjects. Nephrogenous cAMP and serum immunoreactive parathyroid hormone levels in the steroid group were significantly higher than those in control subjects (p less than 0.001). Nephrogenous cAMP in the steroid group correlated positively with prednisolone dosage (r = 0.424, p less than 0.01), and most patients who showed obvious elevations of nephrogenous cAMP had received over 10 mg/day of prednisolone for at least 2 mo. Fasting urinary calcium in the steroid group [166.1 +/- 78.5 (+/- SD) mg/g creatinine] was about 2 times greater than that in control subjects (74.1 +/- 35.6) (p less than 0.001). Fasting urinary calcium in control subjects correlated negatively with nephrogenous cAMP (r = -0.486, p less than 0.02). In contrast, these values in steroid group showed significant positive correlation (r = 0.631, p less than 0.001), suggesting that increased urinary calcium excretion is an important factor in the development of secondary hyperparathyroidism. Elevated nephrogenous cAMP and serum immunoreactive parathyroid hormone levels decreased after the administration of trichlormethiazide and/or 1 alpha hydroxy-vitamin D3. We conclude that increased urinary calcium excretion plays an important role in the development of secondary hyperparathyroidism in patients under glucocorticoid therapy and that the administration of thiazide and/or vitamin D could improve the secondary hyperparathyroidism caused by glucocorticoid therapy.