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Biomedical subjects

E R Yendt

Publications and source records attributed to E R Yendt.

At least 19 recordsLinked to original sources
PubMed1994

Primary hyperparathyroidism masked by antituberculous therapy-induced vitamin D deficiency.

Antituberculous chemotherapy agents, particularly rifampicin and isoniazid, affect vitamin D metabolism and can create biochemical evidence of vitamin D deficiency. Vitamin D deficiency induces a state of resistance to parathyroid hormone. This study sought to explain the temporary resolution of hypercalcaemia and hypercalciuria, during antituberculous chemotherapy with rifampicin and isoniazid, in a subject with a surgically proven parathyroid adenoma and coincidental spinal tuberculosis. Serum ionized calcium, 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D, plasma parathyroid hormone, and 24-hour urine excretions of calcium, inorganic phosphorus and hydroxyproline were sequentially measured over a 3-year interval that included 18 months of antituberculous chemotherapy. Initial serum ionized calcium was 1.52 mmol/l (normal 1.20-1.35 mmol/l), 24-hour urine calcium excretion was 9.40 mmol/day (normal 1.25 to 7.50 mmol/day) and plasma intact PTH was 9.2 pmol/l (normal 0.0-4.5 pmol/l). During antituberculous chemotherapy the serum ionized calcium and 24-hour urine calcium excretion were normal but the plasma PTH rose to higher levels. Following completion of the chemotherapy, hypercalcaemia and hypercalciuria returned with levels similar to those observed pretreatment. Serum 25-hydroxyvitamin D was low at 6.25 nmol/l (normal 20 to 90 nmol/l) during antituberculous chemotherapy, but was normal before and after. Serum 1,25-dihydroxyvitamin D was normal throughout the 3-year interval. We conclude that the antituberculous chemotherapy induced relative vitamin D deficiency and resistance to parathyroid hormone action, thereby masking the hyperparathyroidism and hypercalcaemia until the chemotherapy was completed.

Adenoma↗
PubMed1993

Reversible parkinsonism induced by hypercalcemia and primary hyperparathyroidism.

We describe a patient who had the recent onset of both primary hyperparathyroidism and parkinsonism. Surgical removal of a parathyroid adenoma was followed by spontaneous resolution of the parkinsonism. Hypoparathyroidism and other disorders of calcium metabolism are recognized causes of secondary parkinsonism, while hyperparathyroidism is not. We review the relevant literature, which supports the hypothesis that hypercalcemia may have induced cytotoxic changes in the basal ganglia of this patient.

Adenoma↗
PubMed1993

Reduced creatinine clearance in primary osteoporosis in women.

We determined the relationship between bone mass and age, anthropometric variables, and serum and urine biochemical variables in 77 normal white women and 37 women with primary osteoporosis, 25 of whom had one or more vertebral compression fractures. Skeletal status was assessed by radiography of the hands with measurement of combined cortical thickness of the second metacarpal bones (CCT) or measurement of radial and lumbar bone density, or by both methods. Radial bone mineral content (RBMC) was measured by single-photon absorptiometry (SPA) and lumbar bone mineral density by dual-photon absorptiometry (DPA). Serum and urine biochemical variables were measured on days 6 and 7 of a controlled diet. In this mixed population of normal and osteoporotic women, we confirmed the strong positive correlation between creatinine clearance (Ccr) and bone mass that we previously reported in normal women. Multiple regression analysis showed that the relationship between Ccr and bone mass of the radius and lumbar spine was independent of age and body stature. Ccr was significantly lower in the 25 osteoporotic women with vertebral crush fractures than in age-matched normal women, and Ccr had predictive value for bone mass in individual subjects. The basis for the relationship between Ccr and bone mass has not been established. We excluded diminished production of 1,25-dihydroxyvitamin D as a result of declining renal function as a possible mechanism.

Absorptiometry, Photon↗
PubMed1991

Bone mass is related to creatinine clearance in normal elderly women.

We determined the relationship between bone mass and age, anthropometric variables, creatinine clearance (Ccr), and serum and urine biochemical variables in 77 normal white women (aged 41-86, mean = 67) living in their own homes. A total of 74 women were postmenopausal. Skeletal status was assessed in all subjects by x-rays of the hand with measurement of the mean combined cortical thickness (CCT) of the second metacarpal bones. In 53 women, bone mineral content of the radial shaft (RMBC) was also measured by single-photon absorptiometry (SPA) and lumbar bone mineral density (LBMD) was measured by dual-photon absorptiometry (DPA). Serum and urine biochemical variables were measured under standardized conditions on the sixth and seventh days of a controlled diet. There was a strong positive correlation between Ccr and bone mass. Although our subjects showed the expected linear decline in Ccr with age, we found that the relationship between Ccr and bone mass in the radius and lumbar spine was independent of age. On the other hand, the relationship between Ccr and CCT was not independent of age. We concluded that the relationship between Ccr and lumbar and radial bone mass is probably indicative of a relationship between glomerular filtration rate and bone mass, although this requires validation with a noncreatinine method for measurement of glomerular filtration rate. Age per se does not appear to be a cause of declining lumbar bone mass after the menopause.

Absorptiometry, Photon↗
PubMed1989

Osteopenia, pathological fractures, and increased urinary calcium excretion in schizophrenic patients with polydipsia.

Ten male chronic schizophrenic patients with polydipsia and 10 nonpolydipsic controls, matched for gender, diagnosis, duration of illness, age, and race, were studied by dual- and single-photon absorptiometry to estimate bone density of the lumbar spine and radius and by 24-hr urine collections to estimate urinary electrolyte excretion. Bone density was normal in the control group, but was abnormally low in the polydipsic group, which had a markedly increased incidence of fractures. Electrolyte excretion was normal in the control group and in the polydipsic group when water intake was restricted to normal amounts; increased urinary sodium and calcium excretion occurred in proportion to polydipsia. As polydipsia is associated with a number of physiological changes, the cause of the osteopenia is unclear; we suggest that a negative calcium balance caused by increased urinary calcium excretion induced by extracellular space expansion may play an important role in the causation of the skeletal changes.

Adult↗
PubMed1989

Clinical and laboratory approaches for evaluation of nephrolithiasis.

The initial part of this presentation deals with the sensitivity of tests commonly used in the diagnosis of primary hyperparathyroidism. Total serum calcium levels often are normal in patients with small parathyroid adenomas but levels of serum ultrafilterable and/or ionized calcium usually are elevated in these patients. The recent introduction of improved radioimmunoassays for measurement of circulating parathyroid hormone has led to greatly improved sensitivity of this test for the diagnosis of primary hyperparathyroidism. However, measurement of total urinary cyclic adenosine monophosphate, even when expressed as a function of glomerular filtration rate, is an extremely insensitive test in patients who have parathyroid adenomas weighing less than 1 gm. Consequently, this test no longer is used for diagnostic purposes in our laboratory. Data relating to the prevalence and causes of hyperoxaluria in patients with idiopathic calcium oxalate stones also are presented. Hyperoxaluria (more than 450 mumol. per 24 hours) was found in 21 of 99 consecutive untreated male patients. Approximately a third of the patients with high normal or increased urinary oxalate excretion also have increased urinary glycolate excretion, which is indicative of increased endogenous oxalate production. This metabolic abnormality was unresponsive to pyridoxine administration but preliminary findings suggest that it may be corrected by restricting dietary protein.

Calcium↗
PubMed1986

The effects of chloroquine on serum 1,25-dihydroxyvitamin D and calcium metabolism in sarcoidosis.

Although corticosteroids are effective in the treatment of hypercalciuria and hypercalcemia in chronic sarcoidosis, complications of their long-term use frequently limit therapy. We studied the efficacy of chloroquine in two patients with sarcoidosis who were unable to tolerate the dosage of corticosteroids required to control hypercalciuria and prevent the formation of renal stones. Over a three-year period, each patient received a 6-month and a 10-month course of oral chloroquine phosphate (500 mg per day) while continuing to receive corticosteroids at a fixed dose. Chloroquine therapy was associated with a significant reduction in levels of serum 1,25-dihydroxyvitamin D (1,25(OH)2D) and urinary calcium. We observed a direct correlation between serum 1,25-(OH)2D levels and 24-hour urinary calcium excretion, supporting the hypothesis that excessive serum 1,25-(OH)2D is responsible for the hypercalciuria in sarcoidosis. Serum levels of 25-hydroxyvitamin D (25-(OH)D) did not change with therapy, suggesting that chloroquine may act by inhibiting the conversion of 25-(OH)D to 1,25-(OH)2D. Current dosage guidelines and ophthalmologic-surveillance techniques, which allow chloroquine to be administered with little risk of retinopathy, should permit an expanded role for this agent in the treatment of the calcium abnormalities of sarcoidosis.

Adrenal Cortex Hormones↗
PubMed1986

Reduced serum calcium and inorganic phosphate levels in normal elderly women.

Because published data on the effect of normal aging on serum calcium and phosphate levels are scanty and contradictory, we measured these parameters in 36 normal women over the age of 65 and compared these values with those obtained previously and concurrently in younger women. We found a significant decline in both serum calcium and phosphate levels after the age of 65. We also measured corrected total serum calcium, serum ultrafiltrable calcium, and serum ionized calcium levels in all of the elderly women and in 29 of the younger women and concluded that the decline in total serum calcium levels seen with aging was attributable in part to decreased levels of protein bound calcium but that there was also a slight reduction of ionic calcium levels. Data obtained in elderly women with proven parathyroid adenomas are included to illustrate how the recognition of these age related changes in total serum calcium levels may aid in the identification of slight but clinically important hypercalcemia in elderly adults.

Adult↗
PubMed1986

Parathyroid exploration for primary hyperparathyroidism.

Parathyroidectomy was studied retrospectively in 107 patients with primary hyperparathyroidism. This condition was diagnosed by measuring both the total serum calcium and ultrafilterable calcium (non-protein-bound) levels. The identification of ultrafilterable calcium is an important adjunct to parathyroid surgery as it allows the diagnosis of hyperparathyroidism when the total serum calcium level is normal. The surgical technique for selective parathyroidectomy and multiple biopsies was uniform. Parathyroid adenoma was discovered in 73 patients, diffuse hyperplasia in 26 and combined disease in 8. Postoperatively, two patients suffered from permanent hypocalcemia and three had hypercalcemia.

Adenoma↗
PubMed1986

Absorptive hyperoxaluria: a new clinical entity--successful treatment with hydrochlorothiazide.

This report describes studies performed over an 11 year period in a 13 year old girl with hyperoxaluria and calcium oxalate nephrolithiasis who did not have primary hyperoxaluria or any of the recognized causes of secondary hyperoxaluria. The patient also had increased urinary excretion of calcium and magnesium and hyperabsorption of dietary calcium and magnesium. It is suggested that the hyperoxaluria resulted from hyperabsorption of dietary oxalate secondary to hyperabsorption of dietary calcium. Hyperabsorption of dietary magnesium and increased urinary magnesium excretion have not previously been reported in this context. Stone formation ceased and urinary oxalate excretion gradually fell to normal during long term thiazide therapy but hyperoxaluria recurred when orthophosphate therapy was substituted for the hydrochlorothiazide. This is the first report of normalization of urine oxalate excretion during thiazide therapy in a patient with frank hyperoxaluria.

Adolescent↗
PubMed1985

Response to a physiologic dose of pyridoxine in type I primary hyperoxaluria.

We measured urinary oxalate and glycolate excretion before and during pyridoxine administration (2 to 200 mg per day) in four patients with primary hyperoxaluria. In two patients with type I primary hyperoxaluria, urinary oxalate and glycolate excretion fell markedly in response to a physiologic dose of pyridoxine of 2 mg per day and became completely normal when the dose was increased to 25 mg per day. In the other two patients, who had a different type of primary hyperoxaluria (normal urinary glycolate excretion), there was no response to 2 mg of pyridoxine per day. In one of these patients, doses of 25 and 50 mg per day were also ineffective, but a moderate reduction in oxalate excretion took place with 200 mg per day; in the other patient there was a moderate reduction in oxalate excretion with 25 mg of pyridoxine per day. Our findings suggest that the degree of hyperoxaluria in this disorder may be only slight or moderate if the patient has been ingesting a pyridoxine-rich diet or multivitamin tablets containing small amounts of pyridoxine. Our results also suggest that smaller doses of pyridoxine than those heretofore employed should be tried in patients with primary hyperoxaluria.

Child↗
PubMed1981

Unsuspected hypercalcemia among adults in hospital.

Physicians usually fail to recognize an abnormal serum calcium level and often do not arrive at a definite conclusion about its cause. Yet hypercalcemia, even when minimal, indicates potentially serious underlying disease. This review of the records of about 12 000 adults in hospital showed a prevalence of unsuspected hypercalcemia of 1.4%, a 24% rate of recognition of the abnormal serum level and a 71% rate of correct diagnosis (though often presumptive) of the underlying cause by the attending physician, and a possible prevalence of unsuspected hyperparathyroidism of 0.3%. Because of other considerations, however, the prevalence estimates are probably for too low.

Adult↗
PubMed1980

Reduction of urine oxalate during long-term thiazide therapy in patients with calcium urolithiasis.

We measured urinary oxalate by the method of Hallson and Rose before and during long-term thiazide therapy in 49 patients with recurrent urolithiasis. Urinary oxalate excretion in normal men and women on their usual diets was 38.8 +/- 10.3 mg per day (mean +/- SD) and in patients with calcific renal calculi was 45.9 +/- 14.3 mg per day. Hydrochlorothiazide produced a significant decrease in urinary oxalate excretion in patients treated for more than 12 months (33 +/- 10.6 mg per day). We believe that the thiazide-induced reduction of urinary oxalate excretion is related to reduced intestinal calcium absorption which has been shown during chronic thiazide therapy and may not be evident until 12 or more months of thiazide administration.

Benzothiadiazines↗
PubMed1978

Prevention of calcium stones with thiazides.

On the basis of almost 15 years of experience with thiazide treatment in 346 patients with calcium stones, we believe that the following conclusions are justified: 1) Stone progression ceases in at least 90% of patients who take hydrochlorothiazide (50 mg, twice daily) on a regular basis. 2) A reduced dose of hydrochlorothiazide, i.e., 25 mg twice daily, appears to be effective in a significant proportion of patients. 3) Thiazides are effective in normocalciuric as well as hypercalciuric patients and in most patients with tubular ectasia (medullary sponge kidney). 4. Side effects necessitate discontinuation of thiazide treatment in approximately 7% of patients. The incidence and severity of side effects is reduced by initiating treatment with a small dose and by increasing the dose progressively until the full maintenance dose is achieved. A trial with a reduced dose is warranted in patients who are unable to tolerate the regular maintenance dose. 5) The therapeutic efficacy of thiazides in stone prevention cannot be accurately predicted by the degree of hypocalciuric response. Stone prevention may cease despite a minimal hypocalciuric response, whereas stone progression may occur when an adequate hypocalciuric response has taken place. 6) In addition to the hypocalciuric action, thiazides reduce urine oxalate excretion and increase urine zinc and (probably) magnesium; these effects probably contribute to the efficacy of this agent in stone prevention.

Animals↗