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Oral calcium tolerance and urinary cyclic amp in urolithiasis
ORAL CALCIUM TOLERANCE AND URINARY CYCLIC AMP IN UROLITHIASIS JAMES H. NELSON, III, h1.D.
KOBEKT A. HEHM.
H E R B E R T IV. RIE>lENSCHNEIDER, BRY.4N PFLUG. PF~. I>. 1f71LLIAAI K. D.HITEIIC)LTSE,
hI.11.
HENRY .4. \\TSt:. II. \I. 11. lc4Y KE~IPI>K.
hI.11.
\I. I).
H.“\
C H E S T E R (:. \VINTFH. \I. 11
From the IXvision of Urology, Ohio State Uni\rcGt!, ‘Ilcdical (:c.nttbl and Riverside Methodist Hospital, Colun~bus, Ohio
The diagnosis of hypercalciuria has traditionall> lx~n made on the basis of twenty-four-hour urinary calcium excretion, however; recoinmended collection methods and normal levels of excretion show remarkable variation 1,). a u t h o r a n d geographical location. ‘-’ Other factors such as dietary calcium, sex. age, sodium intake. physicul activit)~, a n d d r u g s can cause variation in normal levels. Individual subjects can show a 20 per c e n t \2riation in excretion of‘ calcium on succtwling days under controlled conditions on a metabolic unit.” Pak and co-workers”*” have described a simple oral calcium tolerance test, with simultaneous determinatiol~ of cyclic AhIP excretion, that has been useful in differentiating a large series of scalectcd p a t i e n t s w i t h dell-documented metabolic ahnormalities causing hypercalciuria. Radioilllinunoassa!. of the nucleotide. cyclic AMP, m’as follnd to be an indicator of parathoril~oiit~ acti\zit!,, i3H and, Lvhen coupled with the drterniination of urinar), calcium hefbre a n d after an oral calcium load, aided in distinguishing hypercalciuria d u e t o hy~~er~~~~r~~th~roidisnl from that of intestinal h~~~erabsorption and renal tubular leak. IVr have undertaken to apply the Pak method to the rolltine evaluation of a largel!’ linselected
s e r i e s o f ptients w i t h s t o n e s SWII ovt~~ ;111 eighteen-month period at this Center. This prospective study was undertaken to ascertain the Ilsefulness of the oral calcium tolerance test (MXT) and urinary cyclic A?rIP (C4SlP) in the differential diagnosis and treatmrwt of patients v*.ith stones in routine urologic practice and to determine their effectivrnws in wlation to more commonl~~ used methods of diagnos~a. ‘Llaterial a n d \lcthocls Sixt)r-one p a t i e n t s w i t h calciuln llrolithiasis seen at this Center and 10 health)-~ control sl11,jccts \vere i n c l u d e d i n the stlld!. (Fig. 1). T\venty-five p a t i e n t s (11 f~malc and 14 ~nales) were studied after the appearancv of’ their first s t o n e ; 36 p a t i e n t s m:ith recurrt~nt stont’s i 11 ft~males a n d 2.5 males) were r,\.aluated. The patitants were n o t sclectcd f o r inanagmlt~nt prob lems or frequenq. of recurrence \+.ith the euccytion of 2 patients referred lwc;iuse of srlspected h~pcrparath~roidisin. Agcbs ranged f r o m t h i r t e e n t o sixt\--se\.en )-ears fbr fern&s and from t\vent!--eight to sixt)r-one fbr males. Control sill)jects were 5 inale p h y s i c i a n s and incdical s t u dents and 5 female nurses railging in age from hvrnty-six t o forty-st‘\,en !.rars. Nonc of thtl cwntrol sllbjects h a d a liistor!. of Ilwlogic 01
P d
q n q
1st STONE RECURRENT STONE 1st STONE
g RECURRENT STONE
renal disease. All experimental subjects had passed stones containing either pure calcium oxalate or predominantly calcium oxalate with minor amounts of calcium phosphate. None had evidence of obstructive uropathy or urinary infection when studied. Patients were evaluated either as inpatients at the participating institutions (early in the study) or as outpatients in the clinics or private office. It became apparent as the study proceeded that all preparation and specimen collection could be done easily on an outpatient basis by the clinic or office nursing staff. Control subjects underwent the oral calcium tolerance test alone. All patients with stones had serial serum calcium, phosphorus, and uric acid in addition to the OC’IT. Additionally, 26 patients had one or more twenty-four-hour urine collections analyzed for calcium, creatinine, protein, uric acid, and in some instances oxalate. Collections were done with patients on a calcium-restricted diet consisting of avoidance of dairy products (approximately 400 mg.) for at least seven days. Serum parathyroid hormone levels were obtained by radioimmunoassay in 26 patients. For the oral calcium tolerance test, patients were maintained on a calcium-restricted diet (approximately 400 mg./day) for at least seven days. Fasting began at 9 P. M. prior to the test, except for 300 ml. of distilled water at 9 P. M. and midnight. On the morning of the test, subjects awoke, voided, and drank 600 ml. of clistilled water. All urine was then collected from 7 A.M. to 9 A. M. when the patients arrived at the
clinic or office. Urine volume was measured, md a 5-ml. specimen was frozen and saved for analysis for calcium, creatinine, a 11 d cyclic AMP. At 9 A. M., after completion of the fasting collection, sulljects drank another 300 ml. of distilled water along with an oral load of 1 Gm. of calcium as calcium gluconogalactoglucoriate (NeoCalglucon) and ate a light, low-sodium, caffeine-free breakfast. Urine was collected again, until 1 P. M. Another 300 ml. of distilled water were taken at 11 .+.hI. The test was terminated at 1 P. M. when the patient returned to the clinic or office. Urine volume was measured again, and a 5-ml. aliquot was frozen and submitted for calcium, creatinine, and cyclic AMP analogs. The OCTT protocol is depicted i n Figure 2. Urinary cyclic AXIP was determined by a standard radioimmunoassa~ technique. Results were plotted on graph paper and compared with the Pak standards for analysis. Fasting and postloading calciums were reported as a ratio of calcium to creatinine (mg./mg.). Urinary cyclic AMP was reported as a ratio of cyclic AhlP to creatinine (@I./Cm.). Statistical analysis was performed by both Students t test and Schefe procedure. Correlation coefficients and scattergrams were employed when indicated. Results Tlcenty-flour-hollr
urinclry ccrlcitlIrl
cxcwtior~
Twelve female and 14 male patients with stones had thirty-six determinations of twcnt).four-hour urinar), calcium excretion. %Llean
9 PM
A. BEGIN FAST
*
7
A ARISE
AM
B 300 ml DISTILLED Ii20
B
VOID
C 6OOml
12 MN
A 300
ml DISTILLED Ii20
DISTILLED H20
D BEGIN URINE COLLECTION 2 HOUR FASTING 9 A M. A ARRIVE AT OFFICE B TERMINATE URINE COLLEC.TION C FREEZE ALIOUOT FOR ANALYSIS Co”, Cr, CAMP D 900 mp
NE0
CALGLUCON
+ 100 mg Ca*BREAKFAST E 3 0 0 m l D I S T I L L E D Ii20 F BEGIN URINE COLLECTION 4 HOUR POST-LOADING I PM
A 300 ml DISTILLED Ii20
A RETURN TO OFFICE - I I A M B TERMINATE URINE COLLECTION C FREEZE ALIQUOT FOR ANALYSIS Co*,
Cr, CAMP
excretion \vas 200 mg.124 h o u r s (t 80 mg. S.D.) f;)r f e m a l e s a n d 2 5 8 mg.124 h o u r s (2 7 0 mg. S.D.) fi)r des. There was a significant differe n c e n o t e d ( p < 0 . 0 5 ) b e t w e e n t h e s e x e s . So significant difference was noted, however, b e t\veen patirants tested after first stones (209 mg./84 h o u r s -C 51 mg. S. D.) and t h o s e t e s t e d after recurrent episodes (248 mg.124 hours 2 92 1ng. s. I). 1.
Radioiminunoassa~ o f s e r u m parathormone (PTH) \vas normal iu all of 7 female and 5 male stone-forming patients after their first stone. Six female a n d 5 male recurreut s t o n e farmers h a d n o r m a l \rall~es f o r PTH. Ele\rated h o r m o n e lr~x~ls were’ found in 3 male patients with recurrc>nt stones. Three of these 5 patients m’ere IX+ ft~rrcd l)ec.aiise o f s u s p i c i o n o f hyperparatli! roidisin a11c1 h a v e h a d adenoinas confirmed at n e c k exploration. The other 2 pat i e n t s \\,ith rle\xted P T H l e v e l s arc mvaiting neck rvq~loration. Tlle)~ a r e n o t iuclutled i n thcl h~pt~‘paratl~~~roid group.
creatinine (2 0 . 0 2 5 nrg.ii~ig. 2 S. E. I. Following a 1-Gm. oral calciuni load, urinar), excretion increased to 0.149 iiig..iiiig. creatinine (k 0.052 nlg./mg. 2 S.E.). T\veut!,-fi\,e patients \vere giveii the oral calcium tolerance test aftei their first stone. The test mxs (101w ;t total of thirty-six times in these patients. Thirty-six recluxnt stone-forming patients unclenrent t h e test fort)--eight times (Table I). It MXS fi)und that recurrent stone-forming patient:; had elevated calcium excretion both in the fastirlg and postloading states. No significant clif‘f;,rc,uctx was seen in the OC’IT results between controls and patients with a first stone or l)>, s(~x. ~ilg./rilg.
T.u3r.rf I. ,ASSAzY
NO
\O\‘E\IBER
I973
i
\~0t,l~3lE
Sll. NC‘klBLSR .5
qclic A,\11 cw7-c~tion stotwv 1 twwtt + 2 S.I:. )
CONTROLGROUP
FIRST
TESTS
t-rsults
IO
2 HOUR (FASTING
“ 6 3
STONE
-wRECURRENi STONE
POST-LOADING
CVCLlC
48
36 I02
(f0025)
(+oozl
II3
(+_.10191
1
AMP
149 (+
(*MOLES Igm
TESTS
2 HOUR t FASTING i
l~Rol,o(:‘I~
unrl
(ittrl rcctm-cwt
C A L C I U M img/mg CREATININE)
NO
111 10 control subjects. two-hour urinary cdcium excrcltion after au overnight f&t \vas 0.063
OC7’1’
c~ftet-first
185 c’ 0 2 4 1
0521
21
POST-LOADING
(+-2
2 42
If 033)
CREATININEI
10 363
2 5 4
17
(+O 9 4
3 19
I
I
/
75
I?
29 08,
2
44
0 431
Ito 44)
2
IO
(‘i’ 35,
.i-7 I
The criteria of Pak,’ based on complex calcium balance studies, were used to assign patients to groups according to OCTI response. Patients with fasting ratios less than 0.110 mg. Caimg. Cr (Pak normal mean + 2 S.D.), but with postloading ratios greater than 0.200 mg. Ca/mg. Cr (Pak normal mean + 2 S.D.) were labeled hyperabsorbers of calcium (absorptive hypercalciuria). Patients with fasting ratios greater than 0.110 mg. Ca/mg. Cr were classed as hyperexcreters of calcium (renal hypercalciuria). The third group was comprised of patients with normal ratios (normocalciuric urolithiasis). These three groups were compared to each other, to controls, and to the three documented hyperparathyroid patients to assess the validity of the divisions. Table II summarizes the makeup of the g r o u p s b y OC’IT results. Fasting calcimn t o creatinine ratios were seen to be significantly elevated in patients assigned to the renal hypercalciuria group when compared with all other groups with the exception of the hyperparathyroidism group. There was a marked elevation of the fasting calcium excretion in hyperparathyroid patients; however, statistical analysis could not distinguish this group from patients with absorptive hypercalciuria. Perhaps expansion of the series will magnify this difference to a level of statistical significance. Oral calcium loading brought out a significant difference between patients with either absorptive or renal hypercalciuria and patients with normocalciuric urolithiasis or controls. Hyperparathyroid patients, although having a markedly abnormal response, could not be clistinT ABLE
II.
ASSAY
OCTT
results and
CONTROLGRQUP
q&c
guished from other groups. OCTT responses in the \,arious grollps are depicted in Table II and Figure 3. No statistical correlation could be folmd between twenty-four-hour calcium excretion and either pre- or postloading calcium to creatinine ratios, Six of 11 (55 per cent) normocalcemic patients (based on maximurn normal twenty-fourhour urinary calcium of 200 mg.) had abnormal O C T T r e s p o n s e s . Conversely, of 14 patients with elevated twenty-four-hour urinary calcium, only 2 (14 per cent) had normal OCTT responses.
Urinary cyclic AMP was determined in 10 normal controls and in 49 patients with stones as part of the OCTT. Normal subjects excreted 3.63 /.~.hl. CA&gP per gram of urinary creatinine (2 2.17 ,uM./G m. 2 S.E.) in the fasting state and 2.42 pM./Gm. (? 0.94 /..&l./Gm. 2 S.E.) after an oral calcium load. Results of cyclic AMP determination in patients with stones by occurrence and metabolic subgroups are depicted in Table II and Figure 3, respectively. No significant differences were f&md in cyclic AX1P excretion between the controls, first and recurrent stones, sexes, or between patients with absorptive hypercalciuria, renal hypercalciuria, hyperparathyroidism, o r normocalciuric urolithiasis. Colnllwllt
Serum calcium and phosphorus determinations remain the best screening tests for hyperparathyroidism. RaclioiInmunoassay of serum
AMP excretion in the metabolic ,dgrotcps j,wan k 2 S.E.)
RENAL HYPERCALCIURIA
PRIMARY HYPERPARATHYROID
INTESTINAL HYPERABSORPTION
NOf?MOCALCIURIC UROLITHIASIS
CALCIUM (mghnq CREATININE) N O . WTIENTS 2 HOUR (FASTING 1
IO
I9
24
I5
,063
( +_ ,025)
,179 ( + .046)
,142 ( z.046)
.082
WST-LOADING .I49
( ’ .052)
,274
.254 ( ’ ,126)
,276 ( 2 ,034)
,137 (2 020)
II
21
CYCLIC AMP (pM0LE.S NO. PATIENTS 2 HOUR (FASTING )
IO 3.63
( ’ ,060)
PO
13)
,069 ( +_ ,010)
/gm CREATININE)
(+2.17
I4 )
POST-LOADING 2.42 (+0.94 )
522
3
2.70
1.83
(+ 1.00)
co.371
3 2.80
2.91
VROLOW
(+0.49)
(ZO.91 1
i
2.16
(+0.49)
1 . 5 9 (+O.
NO\‘EMHER
lY7N
32 1
/ \.OLI’hlE
3.03
ci.02,
2.06
(20.55
SII.
NI’hlHEK
)
5
ca/cr (mqhq) 50
FASTING
POST LaPDING
CAMP/Cr (puMOLES/qml IO
40
El
30
6
20
4
IO
2
Co/O !mq/mg)
POST LOADING
FASTING
FASTING
POST LOADING
CAMP/‘Cr (,uMOLES /ar )
40
8
30
6
FASTING
POST LOADING
ca/cr
CAMP/Cr imq/mq) (phWLES/qm) - 5 0 lo-
FASTING
POST LOADING
-40
30
8-
co/cr
lmq/mq)
POST LOADING
FASnNG
FASTING
6-
‘.
‘\
-40
FASTING
8
POST LOADING
. ‘\
‘\
204-
‘\ < ‘. ‘..
IO
<
2-
POST LOADING
CAMPICr
~flMOtES~‘qrn)
c _.____- ___-.---f
Co/Cr (mq/mql 50
POST LOADING
cam
CAMP/Cr (&h+OLES/qm) IO
40
8
30
6
20
4
IO
2
FASTING
(mq/mq) 50
POST LOADING
~>~~r~~thorrncln~ as well as determination of serum i o n i z e d cdt~irim h a v e d o n e ml~ch t o iinprovr precision in diagnosis, however, these tests arc inlpractical fb screening purposes. The twentyfklr-hollr 11rinary calcium excretion rate. though
FASTING
POST LOADING
CAMP/C 1’ (,uMOLES/~m) IO
40
El
SO
6
widely usd. has too often heen iliisleading due t o confusiori o v e r n o r m a l \ dues and clicltar!preparation. Norn~ocalcemic p a t i e n t s \vitll recurrent urolithiasis have generall:r lwtw traded einpiricall~~ 11!- a t t e m p t i n g t o inl:Lrc,astl urinar!
calcimn salt solubility, decrease concentration, or lower pH. The work of Pak with oral calcium loading to differentiate metabolic causes of hypercalciuria has opened the door to more specific treatment. The present study was undertaken to evaluate the facility by which the OCIT could be applied to the routine workup of calcium stone-forming patients. The OCTT was originally described for evaluation of patients with documented “hypercalwere ciuria. ” Metabolic derangements confirmed with a variety of complex techniques. The authors have extended the test to evaluate patients with stones without regard to twentyfour-hour urinary calcium values. No correlation was found between results of twenty-four-hour urinary calcium excretion and OCTT results. Abnormalities of calcium tolerance were found in 55 per cent of normocalcemic patients with stones. The OCTT would thus appear to be more sensitive than the simple twenty-four-hour collection for discriminating between normal and abnormal calcium metabolism. The relationship might be compared with that between a single blood sugar determination and the three-hour glucose tolerance test. The finding that the OCTT is unlikely to be abnormal following a first stone is not surprising, as it is known that urolithiasis is usually an isolated occurrence. Notably, however, 9 of the 25 patients examined after a first stone were found to have abnormalities. Although first and recurrent stones were not statistically different, this incidence of abnormalities along with the ease of examination and low cost, makes the OC7T useful even for first episodes. Oral calcium tolerance testing defined abnormalities in the majority (58 per cent) of patients with recurrent urolithiasis. The results of the present study are in agreement with those of Pak, with notable exceptions. The OC’IT was found to be useful regardless of twenty-four-hour calcium. Cyclic AMP was not found to be a useful test in conjunction with the OCIT. Cyclic AMP was found to be normal in all groups tested including hyperparathyroidism. Therefore, patients with elevation of both fasting and postloading ratios
were subjected to parathormone assay. It is passible that the difference reflects the lack of patient selection in the present study. Continuation of the study may make differences more apparent. Conclusion The oral calcium tolerance test was useful in distinguishing abnormalities of calcium metabolism in patients with calcium urolithiasis. It should be used in conjunction with serial serum calcium, phosphorus, and uric acid determinations to screen patients for hyperparathyroidism, absorptive hypercalciuria, and renal hyperexcretion of calcium. Testing is easily done on outpatients with a minimum of preparation and should help to select patients for more specific medical therapy of the stoneforming diathesis. Urinary cyclic AMP was not fomld to be useful in evaluating parathyroid function. 456 Clinic Drive Columbus, Ohio 43210 (DR. NELSON) ACKNOWLEDGSIENT. To Mrs. Beverly Phillips, R.N., for performing many of the outpatient OC’ITs, and to Thomas Skillman, M.D. and Charles Pak, M.D. for many helpful comments and suggestions.
Heferences 1. Peacock M, Hodgkinson A, and Nordin BEC: Importance of dietav calcium in the definition of hypercalciuria, Br. Med. J. 3: _
469 (l&7).
2. Albright F: Idiopathic hypercalciuria (a preliminary report), Proc. R. Sot. Med. 46: 1077 11953). 3. Nordin BEC, Hodgkinson A, and Peacock M: The measurement and meaning of urinary calcium, Clin. Orthoped. 52: 293 (1967). 4. Alhright F, and Reifenstein EC: Parathyroid Glands and .\letabolic Bone Disease, Baltimore, Williams and Wilkins (1948). 5. Pak CYC, ct al: A simple test for the diagnosis of absorptive, resorptive, and renal hyprrcalciurias, N. Engl. J. Med. 292: 497 (1975). 6. Pak CYC, Data 51, Lawrence EC, and Snyder W’: The hypercalciurias, causes, parathyroid functions, and diagnostic criteria, J. Clin. Invest. 54: 387 (1947). 7. Rush WH, Boyce WH, and Resnick XII: Cyclic adenosine monophosphate; relationship to calcium metal&m and renal lithiasis, J. Ural. 117: 150 (1977). 8. Dohan PH, ct al. Evaluation of urinary cyclic 3’,5’-adenosinr monophosphate excretion in the differential d&n&s of hypercalcemia, J. Clin. Endocrinol. ~letahol. 35: 775 (1972).
VROLOGY
/ NOVEMBER
1978
/ VOLUME
XII. NUMBER 5
KOBEKT A. HEHM.
H E R B E R T IV. RIE>lENSCHNEIDER, BRY.4N PFLUG. PF~. I>. 1f71LLIAAI K. D.HITEIIC)LTSE,
hI.11.
HENRY .4. \\TSt:. II. \I. 11. lc4Y KE~IPI>K.
hI.11.
\I. I).
H.“\
C H E S T E R (:. \VINTFH. \I. 11
From the IXvision of Urology, Ohio State Uni\rcGt!, ‘Ilcdical (:c.nttbl and Riverside Methodist Hospital, Colun~bus, Ohio
The diagnosis of hypercalciuria has traditionall> lx~n made on the basis of twenty-four-hour urinary calcium excretion, however; recoinmended collection methods and normal levels of excretion show remarkable variation 1,). a u t h o r a n d geographical location. ‘-’ Other factors such as dietary calcium, sex. age, sodium intake. physicul activit)~, a n d d r u g s can cause variation in normal levels. Individual subjects can show a 20 per c e n t \2riation in excretion of‘ calcium on succtwling days under controlled conditions on a metabolic unit.” Pak and co-workers”*” have described a simple oral calcium tolerance test, with simultaneous determinatiol~ of cyclic AhIP excretion, that has been useful in differentiating a large series of scalectcd p a t i e n t s w i t h dell-documented metabolic ahnormalities causing hypercalciuria. Radioilllinunoassa!. of the nucleotide. cyclic AMP, m’as follnd to be an indicator of parathoril~oiit~ acti\zit!,, i3H and, Lvhen coupled with the drterniination of urinar), calcium hefbre a n d after an oral calcium load, aided in distinguishing hypercalciuria d u e t o hy~~er~~~~r~~th~roidisnl from that of intestinal h~~~erabsorption and renal tubular leak. IVr have undertaken to apply the Pak method to the rolltine evaluation of a largel!’ linselected
s e r i e s o f ptients w i t h s t o n e s SWII ovt~~ ;111 eighteen-month period at this Center. This prospective study was undertaken to ascertain the Ilsefulness of the oral calcium tolerance test (MXT) and urinary cyclic A?rIP (C4SlP) in the differential diagnosis and treatmrwt of patients v*.ith stones in routine urologic practice and to determine their effectivrnws in wlation to more commonl~~ used methods of diagnos~a. ‘Llaterial a n d \lcthocls Sixt)r-one p a t i e n t s w i t h calciuln llrolithiasis seen at this Center and 10 health)-~ control sl11,jccts \vere i n c l u d e d i n the stlld!. (Fig. 1). T\venty-five p a t i e n t s (11 f~malc and 14 ~nales) were studied after the appearancv of’ their first s t o n e ; 36 p a t i e n t s m:ith recurrt~nt stont’s i 11 ft~males a n d 2.5 males) were r,\.aluated. The patitants were n o t sclectcd f o r inanagmlt~nt prob lems or frequenq. of recurrence \+.ith the euccytion of 2 patients referred lwc;iuse of srlspected h~pcrparath~roidisin. Agcbs ranged f r o m t h i r t e e n t o sixt\--se\.en )-ears fbr fern&s and from t\vent!--eight to sixt)r-one fbr males. Control sill)jects were 5 inale p h y s i c i a n s and incdical s t u dents and 5 female nurses railging in age from hvrnty-six t o forty-st‘\,en !.rars. Nonc of thtl cwntrol sllbjects h a d a liistor!. of Ilwlogic 01
P d
q n q
1st STONE RECURRENT STONE 1st STONE
g RECURRENT STONE
renal disease. All experimental subjects had passed stones containing either pure calcium oxalate or predominantly calcium oxalate with minor amounts of calcium phosphate. None had evidence of obstructive uropathy or urinary infection when studied. Patients were evaluated either as inpatients at the participating institutions (early in the study) or as outpatients in the clinics or private office. It became apparent as the study proceeded that all preparation and specimen collection could be done easily on an outpatient basis by the clinic or office nursing staff. Control subjects underwent the oral calcium tolerance test alone. All patients with stones had serial serum calcium, phosphorus, and uric acid in addition to the OC’IT. Additionally, 26 patients had one or more twenty-four-hour urine collections analyzed for calcium, creatinine, protein, uric acid, and in some instances oxalate. Collections were done with patients on a calcium-restricted diet consisting of avoidance of dairy products (approximately 400 mg.) for at least seven days. Serum parathyroid hormone levels were obtained by radioimmunoassay in 26 patients. For the oral calcium tolerance test, patients were maintained on a calcium-restricted diet (approximately 400 mg./day) for at least seven days. Fasting began at 9 P. M. prior to the test, except for 300 ml. of distilled water at 9 P. M. and midnight. On the morning of the test, subjects awoke, voided, and drank 600 ml. of clistilled water. All urine was then collected from 7 A.M. to 9 A. M. when the patients arrived at the
clinic or office. Urine volume was measured, md a 5-ml. specimen was frozen and saved for analysis for calcium, creatinine, a 11 d cyclic AMP. At 9 A. M., after completion of the fasting collection, sulljects drank another 300 ml. of distilled water along with an oral load of 1 Gm. of calcium as calcium gluconogalactoglucoriate (NeoCalglucon) and ate a light, low-sodium, caffeine-free breakfast. Urine was collected again, until 1 P. M. Another 300 ml. of distilled water were taken at 11 .+.hI. The test was terminated at 1 P. M. when the patient returned to the clinic or office. Urine volume was measured again, and a 5-ml. aliquot was frozen and submitted for calcium, creatinine, and cyclic AMP analogs. The OCTT protocol is depicted i n Figure 2. Urinary cyclic AXIP was determined by a standard radioimmunoassa~ technique. Results were plotted on graph paper and compared with the Pak standards for analysis. Fasting and postloading calciums were reported as a ratio of calcium to creatinine (mg./mg.). Urinary cyclic AMP was reported as a ratio of cyclic AhlP to creatinine (@I./Cm.). Statistical analysis was performed by both Students t test and Schefe procedure. Correlation coefficients and scattergrams were employed when indicated. Results Tlcenty-flour-hollr
urinclry ccrlcitlIrl
cxcwtior~
Twelve female and 14 male patients with stones had thirty-six determinations of twcnt).four-hour urinar), calcium excretion. %Llean
9 PM
A. BEGIN FAST
*
7
A ARISE
AM
B 300 ml DISTILLED Ii20
B
VOID
C 6OOml
12 MN
A 300
ml DISTILLED Ii20
DISTILLED H20
D BEGIN URINE COLLECTION 2 HOUR FASTING 9 A M. A ARRIVE AT OFFICE B TERMINATE URINE COLLEC.TION C FREEZE ALIOUOT FOR ANALYSIS Co”, Cr, CAMP D 900 mp
NE0
CALGLUCON
+ 100 mg Ca*BREAKFAST E 3 0 0 m l D I S T I L L E D Ii20 F BEGIN URINE COLLECTION 4 HOUR POST-LOADING I PM
A 300 ml DISTILLED Ii20
A RETURN TO OFFICE - I I A M B TERMINATE URINE COLLECTION C FREEZE ALIQUOT FOR ANALYSIS Co*,
Cr, CAMP
excretion \vas 200 mg.124 h o u r s (t 80 mg. S.D.) f;)r f e m a l e s a n d 2 5 8 mg.124 h o u r s (2 7 0 mg. S.D.) fi)r des. There was a significant differe n c e n o t e d ( p < 0 . 0 5 ) b e t w e e n t h e s e x e s . So significant difference was noted, however, b e t\veen patirants tested after first stones (209 mg./84 h o u r s -C 51 mg. S. D.) and t h o s e t e s t e d after recurrent episodes (248 mg.124 hours 2 92 1ng. s. I). 1.
Radioiminunoassa~ o f s e r u m parathormone (PTH) \vas normal iu all of 7 female and 5 male stone-forming patients after their first stone. Six female a n d 5 male recurreut s t o n e farmers h a d n o r m a l \rall~es f o r PTH. Ele\rated h o r m o n e lr~x~ls were’ found in 3 male patients with recurrc>nt stones. Three of these 5 patients m’ere IX+ ft~rrcd l)ec.aiise o f s u s p i c i o n o f hyperparatli! roidisin a11c1 h a v e h a d adenoinas confirmed at n e c k exploration. The other 2 pat i e n t s \\,ith rle\xted P T H l e v e l s arc mvaiting neck rvq~loration. Tlle)~ a r e n o t iuclutled i n thcl h~pt~‘paratl~~~roid group.
creatinine (2 0 . 0 2 5 nrg.ii~ig. 2 S. E. I. Following a 1-Gm. oral calciuni load, urinar), excretion increased to 0.149 iiig..iiiig. creatinine (k 0.052 nlg./mg. 2 S.E.). T\veut!,-fi\,e patients \vere giveii the oral calcium tolerance test aftei their first stone. The test mxs (101w ;t total of thirty-six times in these patients. Thirty-six recluxnt stone-forming patients unclenrent t h e test fort)--eight times (Table I). It MXS fi)und that recurrent stone-forming patient:; had elevated calcium excretion both in the fastirlg and postloading states. No significant clif‘f;,rc,uctx was seen in the OC’IT results between controls and patients with a first stone or l)>, s(~x. ~ilg./rilg.
T.u3r.rf I. ,ASSAzY
NO
\O\‘E\IBER
I973
i
\~0t,l~3lE
Sll. NC‘klBLSR .5
qclic A,\11 cw7-c~tion stotwv 1 twwtt + 2 S.I:. )
CONTROLGROUP
FIRST
TESTS
t-rsults
IO
2 HOUR (FASTING
“ 6 3
STONE
-wRECURRENi STONE
POST-LOADING
CVCLlC
48
36 I02
(f0025)
(+oozl
II3
(+_.10191
1
AMP
149 (+
(*MOLES Igm
TESTS
2 HOUR t FASTING i
l~Rol,o(:‘I~
unrl
(ittrl rcctm-cwt
C A L C I U M img/mg CREATININE)
NO
111 10 control subjects. two-hour urinary cdcium excrcltion after au overnight f&t \vas 0.063
OC7’1’
c~ftet-first
185 c’ 0 2 4 1
0521
21
POST-LOADING
(+-2
2 42
If 033)
CREATININEI
10 363
2 5 4
17
(+O 9 4
3 19
I
I
/
75
I?
29 08,
2
44
0 431
Ito 44)
2
IO
(‘i’ 35,
.i-7 I
The criteria of Pak,’ based on complex calcium balance studies, were used to assign patients to groups according to OCTI response. Patients with fasting ratios less than 0.110 mg. Caimg. Cr (Pak normal mean + 2 S.D.), but with postloading ratios greater than 0.200 mg. Ca/mg. Cr (Pak normal mean + 2 S.D.) were labeled hyperabsorbers of calcium (absorptive hypercalciuria). Patients with fasting ratios greater than 0.110 mg. Ca/mg. Cr were classed as hyperexcreters of calcium (renal hypercalciuria). The third group was comprised of patients with normal ratios (normocalciuric urolithiasis). These three groups were compared to each other, to controls, and to the three documented hyperparathyroid patients to assess the validity of the divisions. Table II summarizes the makeup of the g r o u p s b y OC’IT results. Fasting calcimn t o creatinine ratios were seen to be significantly elevated in patients assigned to the renal hypercalciuria group when compared with all other groups with the exception of the hyperparathyroidism group. There was a marked elevation of the fasting calcium excretion in hyperparathyroid patients; however, statistical analysis could not distinguish this group from patients with absorptive hypercalciuria. Perhaps expansion of the series will magnify this difference to a level of statistical significance. Oral calcium loading brought out a significant difference between patients with either absorptive or renal hypercalciuria and patients with normocalciuric urolithiasis or controls. Hyperparathyroid patients, although having a markedly abnormal response, could not be clistinT ABLE
II.
ASSAY
OCTT
results and
CONTROLGRQUP
q&c
guished from other groups. OCTT responses in the \,arious grollps are depicted in Table II and Figure 3. No statistical correlation could be folmd between twenty-four-hour calcium excretion and either pre- or postloading calcium to creatinine ratios, Six of 11 (55 per cent) normocalcemic patients (based on maximurn normal twenty-fourhour urinary calcium of 200 mg.) had abnormal O C T T r e s p o n s e s . Conversely, of 14 patients with elevated twenty-four-hour urinary calcium, only 2 (14 per cent) had normal OCTT responses.
Urinary cyclic AMP was determined in 10 normal controls and in 49 patients with stones as part of the OCTT. Normal subjects excreted 3.63 /.~.hl. CA&gP per gram of urinary creatinine (2 2.17 ,uM./G m. 2 S.E.) in the fasting state and 2.42 pM./Gm. (? 0.94 /..&l./Gm. 2 S.E.) after an oral calcium load. Results of cyclic AMP determination in patients with stones by occurrence and metabolic subgroups are depicted in Table II and Figure 3, respectively. No significant differences were f&md in cyclic AX1P excretion between the controls, first and recurrent stones, sexes, or between patients with absorptive hypercalciuria, renal hypercalciuria, hyperparathyroidism, o r normocalciuric urolithiasis. Colnllwllt
Serum calcium and phosphorus determinations remain the best screening tests for hyperparathyroidism. RaclioiInmunoassay of serum
AMP excretion in the metabolic ,dgrotcps j,wan k 2 S.E.)
RENAL HYPERCALCIURIA
PRIMARY HYPERPARATHYROID
INTESTINAL HYPERABSORPTION
NOf?MOCALCIURIC UROLITHIASIS
CALCIUM (mghnq CREATININE) N O . WTIENTS 2 HOUR (FASTING 1
IO
I9
24
I5
,063
( +_ ,025)
,179 ( + .046)
,142 ( z.046)
.082
WST-LOADING .I49
( ’ .052)
,274
.254 ( ’ ,126)
,276 ( 2 ,034)
,137 (2 020)
II
21
CYCLIC AMP (pM0LE.S NO. PATIENTS 2 HOUR (FASTING )
IO 3.63
( ’ ,060)
PO
13)
,069 ( +_ ,010)
/gm CREATININE)
(+2.17
I4 )
POST-LOADING 2.42 (+0.94 )
522
3
2.70
1.83
(+ 1.00)
co.371
3 2.80
2.91
VROLOW
(+0.49)
(ZO.91 1
i
2.16
(+0.49)
1 . 5 9 (+O.
NO\‘EMHER
lY7N
32 1
/ \.OLI’hlE
3.03
ci.02,
2.06
(20.55
SII.
NI’hlHEK
)
5
ca/cr (mqhq) 50
FASTING
POST LaPDING
CAMP/Cr (puMOLES/qml IO
40
El
30
6
20
4
IO
2
Co/O !mq/mg)
POST LOADING
FASTING
FASTING
POST LOADING
CAMP/‘Cr (,uMOLES /ar )
40
8
30
6
FASTING
POST LOADING
ca/cr
CAMP/Cr imq/mq) (phWLES/qm) - 5 0 lo-
FASTING
POST LOADING
-40
30
8-
co/cr
lmq/mq)
POST LOADING
FASnNG
FASTING
6-
‘.
‘\
-40
FASTING
8
POST LOADING
. ‘\
‘\
204-
‘\ < ‘. ‘..
IO
<
2-
POST LOADING
CAMPICr
~flMOtES~‘qrn)
c _.____- ___-.---f
Co/Cr (mq/mql 50
POST LOADING
cam
CAMP/Cr (&h+OLES/qm) IO
40
8
30
6
20
4
IO
2
FASTING
(mq/mq) 50
POST LOADING
~>~~r~~thorrncln~ as well as determination of serum i o n i z e d cdt~irim h a v e d o n e ml~ch t o iinprovr precision in diagnosis, however, these tests arc inlpractical fb screening purposes. The twentyfklr-hollr 11rinary calcium excretion rate. though
FASTING
POST LOADING
CAMP/C 1’ (,uMOLES/~m) IO
40
El
SO
6
widely usd. has too often heen iliisleading due t o confusiori o v e r n o r m a l \ dues and clicltar!preparation. Norn~ocalcemic p a t i e n t s \vitll recurrent urolithiasis have generall:r lwtw traded einpiricall~~ 11!- a t t e m p t i n g t o inl:Lrc,astl urinar!
calcimn salt solubility, decrease concentration, or lower pH. The work of Pak with oral calcium loading to differentiate metabolic causes of hypercalciuria has opened the door to more specific treatment. The present study was undertaken to evaluate the facility by which the OCIT could be applied to the routine workup of calcium stone-forming patients. The OCTT was originally described for evaluation of patients with documented “hypercalwere ciuria. ” Metabolic derangements confirmed with a variety of complex techniques. The authors have extended the test to evaluate patients with stones without regard to twentyfour-hour urinary calcium values. No correlation was found between results of twenty-four-hour urinary calcium excretion and OCTT results. Abnormalities of calcium tolerance were found in 55 per cent of normocalcemic patients with stones. The OCTT would thus appear to be more sensitive than the simple twenty-four-hour collection for discriminating between normal and abnormal calcium metabolism. The relationship might be compared with that between a single blood sugar determination and the three-hour glucose tolerance test. The finding that the OCTT is unlikely to be abnormal following a first stone is not surprising, as it is known that urolithiasis is usually an isolated occurrence. Notably, however, 9 of the 25 patients examined after a first stone were found to have abnormalities. Although first and recurrent stones were not statistically different, this incidence of abnormalities along with the ease of examination and low cost, makes the OC7T useful even for first episodes. Oral calcium tolerance testing defined abnormalities in the majority (58 per cent) of patients with recurrent urolithiasis. The results of the present study are in agreement with those of Pak, with notable exceptions. The OC’IT was found to be useful regardless of twenty-four-hour calcium. Cyclic AMP was not found to be a useful test in conjunction with the OCIT. Cyclic AMP was found to be normal in all groups tested including hyperparathyroidism. Therefore, patients with elevation of both fasting and postloading ratios
were subjected to parathormone assay. It is passible that the difference reflects the lack of patient selection in the present study. Continuation of the study may make differences more apparent. Conclusion The oral calcium tolerance test was useful in distinguishing abnormalities of calcium metabolism in patients with calcium urolithiasis. It should be used in conjunction with serial serum calcium, phosphorus, and uric acid determinations to screen patients for hyperparathyroidism, absorptive hypercalciuria, and renal hyperexcretion of calcium. Testing is easily done on outpatients with a minimum of preparation and should help to select patients for more specific medical therapy of the stoneforming diathesis. Urinary cyclic AMP was not fomld to be useful in evaluating parathyroid function. 456 Clinic Drive Columbus, Ohio 43210 (DR. NELSON) ACKNOWLEDGSIENT. To Mrs. Beverly Phillips, R.N., for performing many of the outpatient OC’ITs, and to Thomas Skillman, M.D. and Charles Pak, M.D. for many helpful comments and suggestions.
Heferences 1. Peacock M, Hodgkinson A, and Nordin BEC: Importance of dietav calcium in the definition of hypercalciuria, Br. Med. J. 3: _
469 (l&7).
2. Albright F: Idiopathic hypercalciuria (a preliminary report), Proc. R. Sot. Med. 46: 1077 11953). 3. Nordin BEC, Hodgkinson A, and Peacock M: The measurement and meaning of urinary calcium, Clin. Orthoped. 52: 293 (1967). 4. Alhright F, and Reifenstein EC: Parathyroid Glands and .\letabolic Bone Disease, Baltimore, Williams and Wilkins (1948). 5. Pak CYC, ct al: A simple test for the diagnosis of absorptive, resorptive, and renal hyprrcalciurias, N. Engl. J. Med. 292: 497 (1975). 6. Pak CYC, Data 51, Lawrence EC, and Snyder W’: The hypercalciurias, causes, parathyroid functions, and diagnostic criteria, J. Clin. Invest. 54: 387 (1947). 7. Rush WH, Boyce WH, and Resnick XII: Cyclic adenosine monophosphate; relationship to calcium metal&m and renal lithiasis, J. Ural. 117: 150 (1977). 8. Dohan PH, ct al. Evaluation of urinary cyclic 3’,5’-adenosinr monophosphate excretion in the differential d&n&s of hypercalcemia, J. Clin. Endocrinol. ~letahol. 35: 775 (1972).
VROLOGY
/ NOVEMBER
1978
/ VOLUME
XII. NUMBER 5