Alkaline Phosphatase and Plasma-25-OH-Vitamin D in Hyperthyroidism

Abstract

Figure. Amount of either estradiol (0) or zeranol (0) added (mols x [10][11][12] that of Shutt (1969). Eight Blackface ewes were used for the study in vivo. Estrous activity was synchronised by thc use of intravaginal progesterone pessaries. On the day of pessary removal 4 ewes were injected with zeranol (4.8 mg). Injections were made daily for 5 days. Blood was sampled twice daily for LH assay (Chesworth 1977). Estrus was detected by a vasectomised ram. Restdts and DiscussionZeranol displaced estradiol from the binding protein, the curves were parallel but the required levels of zeranol were about five times greater. Korenman (1969) suggested that the relative efficacy of most estrogens in binding to uterine receptors approximates to their biological potcncy. Upon this basis zeranol appears to be relatively potent.After zeranol injection aU ewes were seen in estrus; treatment did not alter the timing or apparent intensity of this. All ewes had elevated LH levels at or near estrus but there were no differences between treatments either in the timing or size of the peak.The results indicate that although zeranol is apparently estrogenic in vitra it has little activity in viva. This discrepancy suggests that either zeranol is a compound whose activity in vitra does not parallel that in vivo or that zeranol is not a competitor but an inhibitor of estradiol binding. The dose used in vivo, over five days, was twice thc size of the normal im plant. The results therefore indicate that, as far as estrogenic activity is concerned, the use of zeranol with breeding females is not likely to lead to adverse effects.Increased alkaline phosphatase is commonly found in patients with hyperthyroidism (Cassar and Joseph 1969) and is generally associated with histological changes in the liver (3, 8). Studies by Chen et al. (2) showed that increased alkalinc phosphatase is at least in part of skeletal origin. In experiments on laying hens with hyperthyroidism Perek anti Snapir (7) demonstra ted increased activity of tissue alkaline phosphatase in epiphyseal cartilage. In the present study the possibility of a causal relationship between increased alkaline phosphatase and vitamin D deficiency was examined. MethodsTriiodothyronine (T 3 ), thyroxine (T4 ) and TSH were determined radioimmunologically. In our laboratory normal values of T 3 are between 0.8 and 1.7 ng/ml, for T 4 between 40 and 120 ng/ml. A TRH-test was performed in patients whose T 3 values were under 3.5 ng/ml or T 4 values were under 140 ng/ml. Those who showed an increase in TSH 30 minutes after injection of 200 ng of TRH were not included in the study. 25-OH-vitamin D (minimum-normal-value = 25 nmol/I) was evaluated with a protein-binding-assay (4). In addition to alkaline phosphatase (maximum norm-level = 180 um, the plasma concentrations of calcium, phosphorus, creatinine and enzyme activities of GOT, GPT and gamma-GT were determined in most patients. Patients whose hyperthyroidism was diagnosed between January 1975 and August 1976 were examined. Not included in t...

The Hydroxylation of Vitamin D on C25 in Thyrotoxicosis The Role of the Activity of Microsomal Liver Enzymes

“…Immediately other investigators conducted estimations of 25OHD 3 plasma levels in thyrotoxicosis. Some of them confirmed our findings but others found normal or slightly increased values [4][5][6][7][8][9]. To explain the variety of 25OHD 3 plasma levels in hy-perthyroidism we moved as follow.…”

Plasma 25-Hydroxyvitamin D and Alkaline Phosphatase Isoenzymes in Hyperthyroidism

“…Other workers have found a significant decrease in 25-0HD in hyperthyroidism (Mosekilde et al, 1977;Valentzas et al, 1977) with mean control values of 70 nmoljl compared with our mean control value of 50 nmol/l. In another study (Hunstein et al, 1977), plasma 25-0HD was below the lower limit of normal (25 nmoljl) in 11 of 20 hyperthyroid patients. However, plasma 25-0HD levels do vary with age (Brown et al, 1976), sex, time of year (Stamp and Pound, 1974), and population (Preece et al, 1973).…”

“…I. Cassar and Joseph, 1969;Chen et al, 1973;Hunstein et al, 1977) including an increase in bone type (Chen et al, 1973). Total AP increases during treatment of hyperthyroidism with antithyroid drugs (Cook et al;1959;Chen et al, 1973), and an increase in bone type can persist for up to nine months after the return to the euthyroid state (Chen et al, 1973).…”

Propranolol and the hypercalcaemia of thyrotoxicosis

“…This may result from negative feed-back due to the higher than normal serum calcium that occurs in hyperthyroidism (Mosekilde et al 1978). Calcium absorption appears to be reduced in hyperthyroidism, possibly due to low plasma 25-hydroxy (25-OH) vitamin D levels (Hunstein et al 1977). Reduced 25-OH vitamin D levels have been attributed (Hunstein et al 1977) to an increased metaboism of vitamin D in thyrotoxi¬ cosis.…”

“…Calcium absorption appears to be reduced in hyperthyroidism, possibly due to low plasma 25-hydroxy (25-OH) vitamin D levels (Hunstein et al 1977). Reduced 25-OH vitamin D levels have been attributed (Hunstein et al 1977) to an increased metaboism of vitamin D in thyrotoxi¬ cosis. This finding has not however been confir¬ med by all groups (Cleeve & Brown 1978) and in addition the effect of hyperthyroidism on other potent metabolites of vitamin D has not to date been studied.…”