Urinary Calcium Excretion During Ketoacidosis of Prolonged
By JACQUELINEGARNETT, E. S. GARNETT, R. J. MARDELL AND D. L. BARNARD Calcium excretion was measured in five grossly obese patients during periods of total starvation of up to 14 weeks. Throughout the starve, all of the patients excreted considerable amounts of calcium and the mean daily calcium loss amounted to as much as 560 mg. There was no association between the urinary calcium
and the urinary sodium, except when sodium was administered. It is suggested that the calcium lost was derived from a labile bone pool, but this was of only minor importance in combating the metabolic acidosis. (Metabolism 19: No. 7, July, 502-508, 1970)
USTAINED NONRENAL METABOLIC ACIDOSIS is uncommon but may occur during prolonged drainage of a pancreatic fistula or in some cases of chronic diarrhoea. It may also be produced by the administration of ammonium chloride. During starvation ketoacidosis develops within two days and persists so long as fasting continues. In this study, changes in calcium “balance” have been followed during the ketoacidosis of total starvation for periods of up to fourteen weeks. MATERIALS AND METHODS One man and four women were studied. Their ages ranged from 21 to 57 years. All were grossly obese with initial weights ranging from 104 to 130 Kg. Apart from obesity, no other abnormalities were found on clinical examination, and biochemical tests of pituitary, adrenal, thyroid and pancreatic function were normal. The patients were studied in a metabolic ward and were ambulant throughout the starve. Their fluid intake was restricted and consisted of tap water, containing 7.0 mg. calcium/100 ml., black tea, black coffee, and salt-free marmite made with tap water. The calcium content of the tap water was checked weekly and was constant. Supplements of vitamin A, B complex and C were given throughout the starve, together with allopurinol (zyloprim) and iron supplements. Urine was collected in 24-hour lots, acidified and deep frozen. Feces were not collected during the starve since patients passed only small amounts of fluid stool about once a week. Urinary calcium and urinary sodium were measured daily using a Unicam SP/90 atomic absorption spectrophotometer. Urinary phosphate was also measured daily using the method of Baginski and Zak.1 Urinary pH and ketone bodies were measured on the second urine passed each day, using narrow range papers and Acetest tablets. Urinary ammonium was measured weekly in all of the patients by a modification of Berthelot’s pheno/hypochiorite From the Department of Nuclear Medicine, McMaster University, Hamilton, Canada. Received for publication February 16, 1970. JACQUELINE GARNETT, MB., B.S.: Clinical Fellow, McMaster University, Hamilton, Canada. E. S. GARNETT, M.B., M.R.C.P. (LoND.), M.R.C.P. (EDIN.): Director, Nuclear Medicine; Associate Professor, Medicine and Radiology, McMaster University, Hamilton, Canada. R. .I. MARDELL, B.Sc.: Biochemist, Wessex Regional Department of Nuclear Medicine, General Hospital, Southampton, England. D. L. BARNARD, B.A., B.M., BCH.: Senior House Physician, General Hospital, Southampton, England.
METABOLISM, VOL. 19, No. 7 (JULY), 1970
Fig. L-Calcium balante during metabolic acidosis. AS.: 20-vear-
old female. Weight before starvation: 104 Kg.; after starvation: 85 Kg. NEGATIVE CALCRJM BALANCE w/d
method and the titratable acidity was measured in all of the patients at varying intervals throughout the latter part of the starve. Weekly measurements of serum calcium were made using an Eppendorf film photometer. Blood hydrogen ion concentration and PCO, were also measured weekly by a capillary Astrup method. Plasma electrolytes, urea, bicarbonate, phosphate and alkaline phosphatase, serum proteins and plasma and urinary creatinine were measured twice weekly by standard AutoAnalyser methods. Before starving began, the patients ate a normal ward diet of unmeasured calcium and phosphate content. During the starve the calcium intake was known accurately since it was derived solely from tap water. It varied with the fluid consumption and ranged from 60-140 mg. per day. A weekly “balance” was calculated by subtracting this calcium intake from the urinary calcium, neglecting any calcium loss in the small quantities of. stool. To investigate the effect of sodium administration, three of the five patients were given a daily dose of SO mEq. sodium for periods ranging from three to five weeks during their period of fasting. (See Figs. 1, 2 and 4.)
RESULTS Before Starvation
The serum calcium was normal in all of the patients and ranged from 9.0 to 9.4 mg./lOO ml. The plasma phosphate was also normal and ranged from 2.6 to 3.9 mg./lOO ml. The alkaline phosphatase, electrophoretic
strips and plasma
BLOOD HYDROGEN ION CONCN
‘\ -.- \\
Fii. 2.-Calcium balante during metabolic acidosis. P.D.: 37-year-old female. Weight before starvation: 110 Kg.; after starvation: 85 Kg.
CALCIUM BALANCE W/d
URNAF~Y SGUUM mEq/d
electrolyte concentration were normal. The blood hydrogen ion concentration, PCOz and plasma bicarbonate were also normal. The blood hydrogen ion concentration ranged from 36 to 44 mEq./L. the PCo.2 ranged from 36 to 40 mm. Hg, and the plasma bicarbonate ranged from 21 to 25 mM/L. The blood urea concentration ranged from 22 to 30 mg./lOO ml. The urinary calcium ranged from 110 to 340 mg./24 hrs., and the urinary phosphate ranged from 680 to 1230 mg./24 hrs. The urinary pH was around 6.5. Glomerular filtration rate, measured as the 24-hour endogenous creatinine clearance, was normal and ranged from 95 to 180 ml./min. None of the patients had significant proteinuria, pyuria or bacteriuria. Radiological surveys of the skeleton were normal in all of the patients. During Starvation
Within 48 hours of starting to fast, ketoacidosis developed in all of the patients and was sustained throughout the fasts with daily urinary concentrations of acetoacetic acid always greater than 50 mg./lOO ml. The blood hydrogen ion concentration rose from a prestarvation mean of 40.0 mEq/L. (normal range 36.0 to 44.0 mEq/L.) to 45.6 mEq./L. by the end of
HYDROGEN ION CONCH
-. /’ /
balance metabolic acidosis. during male. SM.:49-year-old Weight before starvation: 114 Kg.; after starvation: 88 Kg.
the first week and thereafter the mean weekly blood hydrogen ion concentration ranged between 45.0 and 50.0 mEq./L. (Figs. l-5). The total carbon dioxide content (TC02) of the plasma feIl from a mean prestarvation value of 23.2 mM/L. (normal range 21.0-30.0 mM/L.) to mean weekly values ranging from 19.8 to 15.9 mM/L. This fall in TCOz was accompanied by a reduction in the PCOz from a mean prestarvation value of 36.9 mm. Hg (normal 36.0 to 44.0 mm. Hg) to mean weekly values ranging from 35.0 to 28.5 mm. Hg. The urinary pH ranged from 5.5 to 6.5 and the titratable acidity in the latter part of the starve ranged from 14 to 32 mEq./day. The 24-hour urinary ammonium excretion was elevated in all of the patients and reached levels as high as 180 mEq./day. The serum calcium fell gradually during starvation to as low as 8.2 mg./lOO ml., but this fall was associated with a reduction in the serum albumin concentration to as low as 2.6 Gm./lOO ml. The calcium balance was negative in all of the patients for the duration of the starve. The greatest loss of calcium occurred between the second and fifth weeks and thereafter diminished in all of the patients (Figs. 1-5). The total amount of calcium lost during the studies ranged from 9 to 16.8 Gm.
GARNETT ET AL.
balante during metabolic acidosis. P.S.: 3%vearold female. Weighi before starvation: 105 Kg.; after starvation: 81 Kg.
400NEGATIVE CALClUM BALANCE W/d
The effect of changes in acid-base balance on calcium metabolism were first studied in pigs by Lamb and Evvard in 1919.2 They found that the administration of a mineral acid caused an increase in urinary calcium although feeding oxidisable acids had no such effect. However, Gamble, Ross, and Tisdal13 found an increase in urinary calcium during a 15-day fast, and Farquharson, Salter and Tibbetts* produced a rise in the urinary calcium by feeding a ketogenic diet to a seven-year-old child. In both these instances an increased production of ketoacids was assumed. Gamble et al. suggested that bone was the major source of the calcium, since the amount excreted during the short fast was greater than could be accounted for by breakdown of protoplasm. More recently Spencer, Lewin and Samachson” have reported daily urinary calcium levels of around 350 mg. during three-week periods of total starvation and they too suggested that this calcium came from bone. In the present study in which starvation was continued for as long as fourteen weeks, the mean daily calcium loss was always considerably greater than the calcium intake. Thus, the daily urinary calcium was as high as 560 mg. in two of the patients at a time when their calcium intake, derived from tap water, was less than 100 mg. It should be stressed that the calcium losses observed do not
HYGFIOGEN ION CONCN
Fig. 5.-Calcium balance during metabolic acidosis. H.C.: 20-year-old female. Weight before starvation: 130 Kg.; after starvation: 99 Kg.
take account of any calcium lost in the faeces. Since the patients passed very small quantities of faeces this additional calcium loss was probably small but it does mean that the true negative calcium balance during starvation was even greater than shown in the figures. It will be seen that the greatest urinary calcium excretion occurred around the third and fourth weeks at a time when the metabolic acidosis was well established. This pattern of excretion is similar to that reported by Lemann, Litzow and Lennon after administration of ammonium chloride to healthy volunteers for 18 days. In Lemann’s study the calcium balance became markedly negative during the third week. Lemann suggested that during a metabolic acidosis the retained acid was first titrated against the extra and intracellular buffer systems and finally against the bone mineral. In this way he explained both the sodium diuresis which occurred in the first days of ammonium chloride administration and the markedly negative calcium balance which occurred later. An initial sodium diuresis similar to that described by Lemann occurred in all of our patients, and it seems probable that this was also a consequence of the development of ketoacidosis.?
It should be stressed that although large quantities of calcium were excreted in the urine during starvation, the amount of hydrogen ion to which the urinary calcium was equivalent was only 800 mEq., whereas the amount of hydrogen ion excreted as ammonium during the fasts was as high as 8000 mEq. Calcium may also be released from bone during total starvation not only as a consequence of the sustained metabolic acidosis but also as a result of bone breakdown associated with a net loss of nitrogen. Thus, a negative nitrogen balance during starvation was described by Drenick et al8 More recently Litvak et al.Q have demonstrated an increase in urinary hydroxyproline during short periods of fasting and they attributed this to an acute loss of bone. It is interesting to note that during total starvation the urinary sodium and calcium do not necessarily parallel each other. Thus, the urinary calcium rises at a time when the sodium excretion is falling and thereafter the urinary calcium continues to rise, reaches a maximum and falls again while the urinary sodium is constant at less than 5 mEq./per day. However, when 50 mEq. of sodium was administered daily for from 3-5 weeks to three of the patients, the calcium excretion did show a small rise which may have been associated with changes in the volume of extracellular fluid. lo Unfortunately, large quantities of sodium could not be used owing to the nausea it produced.
ACKNOWLEDGMENTS We thank the Wessex Regional Hospital Board for a grant to E.S.G. We also thank those physicians in the Wessex Region who referred patients, Dr. J. Middleton and the staff of the Department of Chemical Pathology for their help with the biochemical measurements, and Mrs. M. Day for her help with the references. REFERENCES 1. Baginski, E., and Zak, B.: Microdetermination of serum phosphate and phospholipids. Clin. Chim. Acta 5:834, 1960. 2. Lamb, A. R., and Evvard, J. M.: The acid base balance in animal nutrition. II. Metabolism studies on the effect of certain organic and mineral acids on swine. .I. Biol. Chem. 37:329, 1919. 3. Gamble, J. L., Ross, G. S., and Tisdall, F. F.: The metabolism of fixed base during fasting. J. Biol. Chem. 57:633, 1923. 4. Farquharson, R. F., Salter, W. T., Tibbetts, D. M., and Aub, J. C.: Studies of calcium and phosphorus metabolism; Effect of ingestion of acid producing substances. J. Clin. Invest. 10:221, 1931. 5. Spencer, H., Lewin, I., and Samachson, J.: Changes in metabolism in obese persons during starvation. Amer. J. Med. 40:27, 1966. 6. Lemann, J., Litzow, J. R., and Lennon,
E. J.: The effects of chronic acid normal man: Further evidence for ticipation of bone mineral in the against chronic metabolic acidosis. Invest. 45 : 1608, 1966.
loads in the pardefence J. Clin.
7. Schloeder, F. X., and Stinebaugh, B. J.: Studies on the natriuresis of fasting. II. Relationship to acidosis. Metabolism 15: 838, 1966. 8. Drenick, E. J., Swendseid, M. E., Blahd, W. H., and Tuttle, S. G.: Prolonged starvation as treatment for severe obesity. JAMA 187:100, 1964. 9. Litvak, J., Wortsman, J., Pumarino, H., and Amendaris, R.: The effect of fasting on urinary calcium and hydroxyproline excretion in obesity. J. Clin. Endocr. 28:3 11, 1968. 10. Epstein, F. H.: Calcium and the kidney. Amer. J. Med. 45:700, 1968.