Calcium metabolism has been investigated in patients with essential hypertension and normal renal function to evaluate the renal calcium handling and the reported increase in renal calcium loss. In 55 hypertensive and 55 sex- and age-matched healthy normotensive subjects creatinine clearance, serum total and ionized calcium, plasma parathyroid hormone and 24 h urinary excretion of calcium, sodium and cAMP were measured. In a subgroup of 20 hypertensive patients and 20 controls the fasting calcium excretion rate was also measured. Both 24 h and fasting calcium excretion rates were higher in the hypertensive group; so also were plasma parathyroid hormone and urinary cAMP. Serum total and ionized calcium levels were not different in the two groups. After intravenous calcium infusion (15 mg 3 h-1 kg-1) in seven hypertensive patients and controls, the hypertensive patients excreted more calcium at all serum calcium concentrations. These results support the hypothesis of primary renal calcium leak in essential hypertension. Enhanced urinary calcium excretion rate may cause compensatory parathyroid overactivity.
We describe a kindred with medullary thyroid carcinoma and phaeochromocytoma (MEN 2A or Sipple's syndrome) in which a cutaneous manifestation is only present in affected members. These members felt an intense itching in an area 5-10 cm in length and passing through the scapular region where, after long-term scratching, the skin appears hyperkeratotic and pigmented. Cutaneous biopsies proved negative for dermis nerve abnormality. This restricted itching strongly suggests dominant transmitted hereditary localized pruritus which was described many years ago in a family which was apparently free from inherited diseases. In the examined kindred this skin peculiarity was said to have appeared before the patients reached 10 years of age and, therefore, prior to the biochemical manifestation of the thyroid tumour. Three children of the last generation, aged 4 to 11 years, all of whom presented this cutaneous manifestation, were considered unaffected because of normal basal and stimulated calcitonin, but thyroid C-cell hyperplasia was recently proved in the eldest. In this MEN 2A kindred the presence of such a characteristic hereditary itch in affected members may be considered as a phenotypic marker giving advance warning of medullary thyroid carcinoma.
A rate of calcitonin decrease less than 50% 30 min after thyroidectomy plus central neck lymph node dissection suggests the persistence of tumor tissue in patients operated for MTC. These results indicate that intraoperative calcitonin monitoring may be a useful tool to predict the completeness of surgery in patients with MTC.
A number of abnormalities in the extracellular and intracellular handling of calcium in arterial hypertension, namely an increased urinary calcium excretion, a reduced serum ionized calcium level and an enhanced intracellular free calcium concentration, have previously been reported by this and other laboratories. The present study aimed to investigate the handling of an exogenous calcium load in hypertensive and normotensive subjects in order to detect possible differences with regard to tissue calcium metabolism in vivo. A constant rate intravenous calcium infusion (0.2 mmol 2 h-1 kg-1 body wt.) was carried out in the participants. Serum calcium concentrations were determined at regular intervals during the infusion and in the 4 h after the end of the calcium load. Over the same period, urinary calcium excretion was evaluated in timed urine collections. Hypertensive subjects had lower serum ionized calcium levels compared with normotensive subjects at all the experimental points, a finding suggestive of a faster disappearance of calcium from the circulation. The total body calcium clearance, calculated from the area under the curve of the serum calcium concentrations, was enhanced in hypertensive patients (P less than 0.03). Although the renal calcium excretion was higher in hypertension, the renal calcium clearance accounted for only a minor fraction of the total body clearance, suggesting that the reduced serum calcium levels achieved by the hypertensive patients were not explained by the renal calcium leak. The enhanced total body calcium clearance found in hypertensive subjects is therefore due to an increased tissue calcium uptake. This finding provides indirect evidence of an altered cell calcium handling in hypertension.
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