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Biomedical subjects

A Racadot

Publications and source records attributed to A Racadot.

At least 109 records · Page 6Linked to original sources
PubMedDate not supplied

[Phosphocalcium metabolism in the elderly. Study of 101 subjects living in an institution].

Calcium and phosphorus metabolism was studied in 101 institutionalized subjects over 70 years of age (mean: 82.5 years). The study was performed in serum and urine; it included parathyroid hormone and calcidiol (250HD3) assays and radiological examination of bones with determination of Meunier's index and metacarpal cortical index. Calcidiol concentrations did not vary with age but were higher in people who left the institution and in men. In contrast, there was a significant age-group related increase of parathyroid hormone concentrations. This increase was accompanied by an increase of parathyroid hormone activity, as shown by a parallel fall in phosphorus reabsorption rate. These findings are in agreement with current pathogenetic theories on senile osteoporosis. Invalid subjects had higher urinary calcium and serum parathyroid hormone levels and a lower cortical index. Paradoxically, there was less vertebral collapse as evaluated by Meunier's index, which may suggest that very old patients develop progressive cortical bone hyperresorption entirely independent of sequelae from their former trabecular osteoporosis.

Aged↗
PubMedDate not supplied

[comparison of the effects on phosphocalcic metabolism and bone of 3 protocols of vitamin D administration in the elderly].

According to recent studies, vitamin D deficiency may contribute to the osteoporosis observed in elderly subjects, with reduced intestinal calcium absorption and secondary hyperparathyroidism. Vitamin D deficiency is often present in elderly people, due to inadequate diet and confinement at home. The administration of either oral vitamin D in doses of 4,000 IU per day, or six-monthly intramuscular injections of ergocalciferol 600,000 IU, combined with a daily intake of at least 1 g of calcium brings back to normal both 25 OH D concentrations and parathyroid hormone levels. When pursued for one year, these treatments also maintain the formation of cortical bone, as shown by the metacarpal index. As for the concentration of 25 OH D, it seems that 60 to 75 nmol/l are necessary to restore calcium homeostasis. The dietary habits of elderly people are such that a supplement of medicinal calcium is required. Finally, we regard the parenteral form of ergocalciferol as being preferable to the oral form at that age for better compliance with treatment.

Administration, Oral↗
PubMedDate not supplied

[Production rate and mean plasma concentration of cortisol in hyperthyroidism (author's transl)].

The adrenocortical function was studied in 23 patients with hyperthyroidism. The half-life of tritiated cortisol was significantly shortened; metabolic clearance rate was about twice increased, and production rate of cortisol was significantly increased in hyperthyroidism. The mean plasma concentration was unmodified. After return to euthyroid state, all the values were normalized in 7 patients.

17-Hydroxycorticosteroids↗
PubMedDate not supplied

[Atrial natriuretic hormone and endocrine functions].

The atrial natriuretic hormone (ANP) is a cardiac hormone which gene and receptors are widely present in the body. Its main function is to lower blood pressure and to control electrolyte homeostasis. Its main targets are the kidney and the cardiovascular system but ANP interacts with many other hormones in order to regulate their secretion. The adrenal glands are the first endocrine target. Steroidogenesis, especially mineralocorticoid synthesis, is inhibited by ANP, but glucocorticoid production seems to be depressed too. As ANP synthesis is enhanced by the latter, it suggests a regulatory loop. Moreover ANP inhibits the thyroid synthesis whereas its production is enhanced by thyroid hormone. The hypothalamo-hypophyseal axis is another important target. ANP inhibits ACTH release and arginine vasopressin secretion. Vasopressin enhances ANP synthesis while GH decreases it. Finally the endocrine effects of ANP strengthen the cardiovascular and renal effects of the hormone, antagonizing the salt and water retention due to aldosterone and AVP. Because of a local production, ANP may also act as a paracrine hormone that influences the function of many endocrine systems (ovarian function for instance). In the central nervous system, ANP acts as a neurotransmitter in order to regulate pituitary and vegetative functions. Plasma ANP levels are impaired in several endocrine diseases : the plasma hormone levels increase in hypercortisolism, hyperaldosteronism, thyrotoxicosis and inappropriate antidiuretic hormone secretion; it decreases in hypothyroidism. In case of Addison's disease, ANP may be used to assess the quality of mineralocorticoid treatment, in association with the other biological criteria.

Adrenal Glands↗
PubMedDate not supplied

[21-hydroxylase autoantibodies as a marker of adrenal involvement in patients with autoimmune endocrinopathies].

Autoantibodies against 21-hydroxylase are common in idiopathic Addison's disease. The objective of this study was to determine the frequency of these antibodies in different endocrine autoimmune diseases with or without adrenal insufficiency and to follow up their evolution. We have used a radiobinding assay based on 125-I labeled 21-hydroxylase (21-OH-AB, RSR, UK). Serum samples with 21-hydroxylase antibodies levels equal or greater than 1.0 U/ml were considered as positive. We found these autoantibodies in 21/23 idiopathic Addisonian patients, in 0/18 patients with isolated hypothyroïdism, in 0/6 patients with isolated Grave's disease, in 2/14 patients with isolated ovarian failure, in 1/27 patients with 2 ou more associated autoimmune diseases without adrenal insufficiency. The comparison between patients with or without adrenal insufficiency has shown, for this assay, a sensibility of 91 %, a specificity of 96 %. The 21-hydroxylase autoantibodies were followed up in 4 patients with Addison's disease and showed progressive decreasing levels. We can not exclude that the addisonian sera might become negative for these antibodies after the total destruction of adrenal cortex. In conclusion, the presence of 21-hydroxylase autoantibodies is highly specific for idiopathic Addison's disease and the level of these antibodies decrease with disease duration.

Addison Disease↗
PubMedDate not supplied

[Proceeding: Production rate, metabolic clearance rate and mean plasma concentration of cortisol in hyperthyroidism (author's transl)].

The adrenocortical function was studied in 23 patients with hyperthyroidism and compared with a group of 15 normal subjects. Parameters of adrenal function were determined with 1,2(3)H-cortisol. The half-life of cortisol is significantly shortened in hyperthyroidism, as compared to normal subjects (49,5 +/- 6,6 min vs 68,3 +/- 10,5 min) and metabolic clearance rate is increased (418,5 +/- 89,5 L/24 h vs 237,5 +/- 48,5 L/24 h, for normal subjects). The production rate of cortisol, calculated from specific and cumulate activities of THE and THF is increased in hyperthyroidism expressed as mg/24 h or mg/m2/24 h (respectively : 26,7 +/- 7,8 mg/24 h vs 15,7 +/- 3 mg/24 h and 16,9 +/- 4,6 mg/m2/24 h vs 9,5 +/- 1,8 mg/m2/24 h). The mean plasma concentration, calculated as the radio (see article) is not statiscally different in hyperthyroid and normal subjects (6,8 +/- 2,1 microg/100 ml vs 7,3 +/- 1,9 microg/100 ml). 7 patients were reinvestigated after treatment of thyrotoxicosis when they were clinically and biologically in euthyroid state. All the values were normalized, without statistically significant difference from control (T 1/2 = 65,4 +/- 18 min, Metb Cl. Rate : 255 +/- 64,5 L/24 h, production rate : 15,6 +/- 1,8 mg/24 h and 9 +/- 1,4 mg/m2/24 h. mean plasma concentration : 6,8 +/- 2,8 microg/100 ml). Shortened cortisol half life, increased metabolic clearance rate and production rate, and normal mean plasma concentration have been reported in hyperthyroidism (Peterson, Copinschi, Gallagher). These changes, secondary to thyroid hormone excess, are the consequences of increased hepatic catabolism of cortisol. The activity of 11 OH steroid deshydrogenase is increased, as demonstrated by increased ratio (see article) in normal subjects (0,001 less than p less than 0,005). There is a high proportion of 17 kéto metabolites (E, DHE, THE) whose feed-back effect is weak as compared to 17 OH metabolites (F, DHF, THF). The hypothalamo-hypophyso-adrenal system is stimulated to maintain a normal plasma concentration. The fact that the mean plasma concentration is normal despite the increased production rate suggest that changes are rather due to increased catabolism than to central effect of thyroid hormones.

Hydrocortisone↗