Ionic fluoride: a study of its physiological variation in man.

The serum ionic fluoride concentrations in 497 normal individuals, from areas with non-fluoridated water supplies, ranged from 0.25 to 2.20 micromol F-/1 and were positively correlated with age (r = 0.31, p less than 0.001). Distribution of the data with age, coupled with the distribution of serum calcium with age, suggests a possible change in bone metabolism between 26 and 35 years of age. Serum fluoride levels vary with the time of day with a mean minimum value at 0800 and a mean peak value at 2200. Renal clearance studies gave fluoride ion clearances ranging from 19.5 to 44.0 ml/min and tubular reabsorption of fluoride ion ranging from 61.5 to 86.5%. After oral ingestion of 0.48 mmol sodium fluoride, peak serum levels occurred at 60 to 90 minutes; the peak levels were significantly higher in women than in men.