SYNOPSISThe relationship between serum ferritin concentration and the amount of storage iron has been studied in normal subjects. A high degree of correlation was demonstrated between serum ferritin concentration and storage iron measured by quantitative phlebotomy. The possible advantages of assessing iron stores by using the serum ferritin concentration are discussed.

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SUMMARY In 52 normal subjects there was an inverse relationship between serum ferritin concentration and iron absorption. In 21 measurements in 15 patients with idiopathic haemochromatosis there was a similar inverse relationship but absorption was higher in relation to iron stores at all levels. Haemochromatotic patients with normal serum ferritin levels had abnormally high values for desferrioxamine chelatable iron and there was no correlation between chelatable iron and iron absorption.Iron balance is maintained by the regulation of iron absorption. The precise mechanism is poorly understood (Jacobs, 1973) and one of the outstanding problems is the relationship of iron stores to absorption. Heinrich (1970) (Bentley and Williams, 1974).More recently, the concentration of ferritin in serum has been shown to relate closely to iron stores in normal subjects and in those with iron deficiency or overload (Jacobs, Miller, Worwood, Beamish, and Wardrop, 1972;Walters, Miller, and Worwood, 1973a;Siimes, Addiego, and Dallman, 1974). The assay of ferritin can be carried out in a reproducible manner on a small serum sample, and a preliminary study indicated an inverse relationship between serum ferritin concentration and iron absorption in normal subjects (Walters, Thompson, Jacobs, and Wood, 1973b). This assay has been used in the present study to confirm the relationship between iron stores and iron absorption in normal subjects and to compare it with data from patients with haemochromatosis.Received for publication 17 October 1974. SubjectsFifty-two healthy adults (22 women and 30 men) were studied. In all cases the serum iron concentration was above 70 jig per dl and the transferrin saturation above 16%. Haemoglobin concentration was above 12-5 g per dl in women and 13-0 g per dl in men.Fifteen patients with primary idiopathic haemochromatosis (one woman and 14 men) were studied; all met the same haematological criteria as the normal subjects. Six of the patients were studied on two occasions giving a total of 21 observations in this group. Three patients were investigated before venesection therapy, nine during and nine after the completion of a course of venesection. Patients studied during treatment were not bled for a minimum of one month before the absorption measurement.All subjects gave their fully informed consent to the investigations. MethodsIron absorption was measured by whole body counting using a flat bed scanning technique. The whole body counter consists of four uncollimated Nal (T1) crystals 10-2 cm thick and 15-2 cm in diameter arranged symmetrically on a vertical metal ring. The subject lies on a fixed bed and the detectors traverse the entire length of the bed. The detectors are connected to a multichannel analyser with 188 on 9 May 2018 by guest. Protected by copyright.

Immersion in water in spas has been practised for centuries and has many proponents. Despite fierce debate about its efficacy there has been little scientific evaluation of the effect of immersion in mineral waters. Eight normal subjects were immersed in Bath spa water for two hours and the renal, haematological, and cardiovascular responses were compared with those in the control periods before and after immersion. Significant, twofold diuresis and natriuresis, 5% haemodilution, and a 50% increase in cardiac index were observed in subjects immersed, sitting, in Bath spa water at 35°C. These changes may constitute part of the scientific rationale for spa treatment in many states of disease.

The renal response to volume expansion produced by water immersion to the neck at 35 degrees C was examined in eight young normotensive uncomplicated insulin-dependent diabetic subjects and in eight matched normal control subjects. Both the diabetic and normal subjects manifested a renal response of natriuresis and kaliuresis on immersion, but the natriuretic response was reduced in the diabetic group. Thus the induced excretion of sodium over the 4 h of immersion was 40 +/- 5 mmol (mean +/- SEM) in the normal group compared with 22 +/- 4 mmol in the diabetic group (P less than 0.02). In the normal subjects creatinine clearance did not change during immersion compared with pre-immersion control values while in the diabetic group it rose from pre-immersion control values of 112 +/- 11 ml/min to a mean value of 127 +/- 11 ml/min during immersion (P less than 0.01). The diabetic subjects thus excreted less sodium despite an increased filtered load during water immersion. Fractional excretion of sodium was significantly reduced in the diabetic subjects compared with the normal control subjects (P less than 0.05). The suppression of plasma renin and aldosterone was similar in normal and diabetic groups. Tubular sodium retention could be an early functional change in the diabetic kidney, and be implicated in the development of diabetic nephropathy.