SUMMARY Plasma 25-hydroxyvitamin D (25-0HD) values in 22 hyperthyroid patients did not differ significantly from those of controls matched for age, sex, and the time of year that plasma samples were taken. In the hyperthyroid group, plasma alkaline phosphatase was significantly higher than in controls, and an increase in bone type alkaline phosphatase occurred in 50 %. In the 18 female hyperthyroid patients the plasma y-glutamyl transferase was significantly increased compared with controls. Mean values for plasma albumin, alanine transferase, and calcium showed no significant difference between hyperthyroid and control patients.Results on the basis of clinical diagnosis supported by an FTI of over 140 (the upper limit of normal for this laboratory). Control patients were those in whom the FTI had been requested by a clinician and were normal. Control patients were matched with hyperthyroid patients for age (± 3 years), sex, and time of year that blood samples were taken (within one month). Patients were excluded from this study if they had received antithyroid therapy before having the blood sample taken or if there was insufficient plasma for all of the analyses to be done. Blood samples were taken over the period July to October 1977.Plasma 25-0HD was measured by a competitive protein binding method (Haddad and Chyu, 1971), modified by the use of diluted human serum as the source of binding protein. Plasma AP isoenzymes were separated by electrophoresis (Cleeve, 1978).Plasma AP, ALT, GGT, FTI, albumin, and calcium were measured by the methods in current use in this laboratory. Calcium values were corrected for the level of plasma albumin (Tomlinson and O'Riordan, 1978). Normal ranges are shown in the Table. There were 18 women and four men in each group, their ages ranging from 19 to 77 years.There were no significant differences in mean plasma 25-0HD, ALT, albumin, and calcium concentrations between the hyperthyroid patients and controls. Two patients in each group had consecutively 25-0HD values below our lower limit of normal. 320Material and methods
Hyperthyroid patients were selectedPlasma 25-hydroxyvitamin D (25-0HD) has been reported (Valentzas et al., 1977) to be markedly reduced in hyperthyroidism, and it was, therefore, suggested that it might be an important clue to our understanding of hyperthyroid bone disease. Other workers (Mosekilde et al., 1977) found that the free thyroxine index (FT!) correlated with the serum 25-0HD, but that the differences between the 25-0HD values in hyperthyroid patients and in controls was not nearly as great. These latter workers found a lack of correlation between serum 25-0HD and bone histomorphometry in hyperthyroidism and concluded that the lowered 25-0HD was of minor importance in the development of hyperthyroid bone disease.Hypercalcaemia occurs in at least 8 % of hyperthyroid patients (Baxter and Bondy, 1966), and in one series 51 % (Mosekilde et al., 1977), the serum calcium being positively correlated with the degree of hyperthyroidism and inversely correlat...