Imogen M. A. Evans

NORMAL PLASMA CALCITONIN: CIRCADIAN VARIATION AND RESPONSE TO STIMULI

A simple, reproducible extraction method has been developed, which is capable of measuring calcitonin in normal individuals. Normal calcitonin levels show a circadian variation, with a peak around midday and respond to known stimuli for calcitonin release.

Pharmacology and Therapeutic Use of Calcitonin

SummaryCalcitonin1 is a peptide hormone secreted by the C-cells of the thyroid gland. A major physiological function of the hormone appears to be the protection of the skeleton against resorption in humans. It thus opposes the resorptive actions of parathyroid hormone and 1,25 dihydroxyvitamin D.This action is utilised pharmacologically in order to treat diseases where increased bone resorption is a major component. The efficacy of calcitonin in the treatment of Paget s disease of bone is well established, especially as it is currently the most effective agent in the treatment of the osteolytic form of the disease. In other bone diseases where resorption of bone is a component it is likely to be worthy of a trial of therapy. There are also sound theoretical reasons why calcitonin may be of benefit in the treatment of certain osteoporoses, especially in combination with other agents. Most recent studies would seem to support this view.A disadvantage of calcitonin therapy is that the hormone has to be administered paren-terally, although future developments may obviate this. It is, however, a form of treatment which is free of any long term serious side effects, and calcitonin now has a definite place in the management of specific bone and calcium disorders.

REGULATION OF VITAMIN D: AN EVOLUTIONARY VIEW

The regulation of vitamin D metabolism by the kidney is now known to be multifactorial. Three regulatory factors are discussed: 1,25(OH)2D3 itself; parathyroid hormone, and phospate. The influence of 1,25(OH)2D3 probably depends on new protein synthesis, while the mode of action of phosphate is unknown. Parathyroid hormone is not essential for regulation but may have an important biological role. The direction of its effect varies, perhaps due to a complex inter‐relation of changes in calcium and phosphorus metabolism and the level of kidney adenyl cyclase activity.

Separation of hydroxylated derivatives of vitamin D3 by high speed liquid chromatography (HSLC).

The recent upsurge of interest in the metabolism of vitamin D3 (cholecalciferol) has relied partly on the use of partition chromatography on Sephadex LH-20 as an analytical tool to separate metabolites [ 1 ] . This system is simple but it is relatively slow and resolution is poor. We present here a method for the separation of hydroxylated derivatives of vitamin D3 using high speed liquid chromatography. First, resolution is orders of magnitude greater: metabolites unresolved on Sephadex LH-20 are separated. Second, an analysis is complete in under 30 min. Third, fractions may also be collected for further studies, e.g. determination of radioactivity. Fourth, continuous monitoring of the column effluent by UV absorption is possible. Further, this technique allows co-chromatography of authentic synthetic compounds with experimentally produced radioactive metabolites to facilitate identification. Using this approach we have confirmed previously the identity of the major metabolite of 25-hydroxycholecalciferol(25-HCC) under conditions of calcium deprivation to be 1,25-dihydroxy-cholecalciferol(l,25-DHCC) by its co-elution with a synthetic sample [23.