Indian J Physiol Pharmacol 1995; 39(4) : 411-414

SERUM CALCIUM, MAGNESIUM AND INORGANIC PHOSPHOROUSLEVELS DURING VARIOUS PHASES OF MENSTRUAL CYCLE

ASHA K. PANDYA*, S. CHANDWANI, TARUN K. DASAND KAUSHIK D. PANDYA

Department of Physiology,Medical College,Baroda - 390 001

( Received on December 6, 1994 )

Abstract: Serum Calcium (Ca), Magnesium (Mg) and Inorganic phosphorous (Pi)were investigated serially during menstrual, follicular, ovulatory and lutealphases of menstrual cycle in 25 healthy medical student volunteers. The resultshows significant cyclic variations within physiological limits in all parameters.Ca level was highest during ovulation (P<O.OOl) and lowest during lutealphase (P<O.OOl)compared to other phases. Exactly opposite result was observedfor Ca level. It is lowest during ovulation (P<O.OOl)and highest during the lutealphase (P<O.OOl). However, the highest level of Pi was seen during menstrualphase (P<O.OOl)and lowest during the luteal phase (P<O.OOl).These changes areprobably brought about under the influence of cyclic variations of the ovarianhormones.

Key words: menstrual cyclemagnesium

INTRODUCTION

Menstrual cycle is a result of complexinteracting processes within the hypothalamus,hypophysis, ovaries and uterus. The cyclicphysiologic changes are mainly brought about bythe ovarian hormones; estrogen and progesterons,the levels of which show variation duringmenstrual cycle.

Effect of ovarian hormones on water andelectrolyte balance is well documented and hasbeen published earlier by the author (1). Estrogenleads to a marked acceleration of Calcium uptakeand decrease of its elimination through pigeon'sgut (2). In non-pregnant women estrogenadministration produces increased parathyroidactivity (3). It is known that the Calciumhomeostasis is maintained by parathyroid glands,However, effect of menstrual cycle on serumCalcium remains controversial (4). It is alsoreviewed that published literature does not assignspecific role to Magnesium in regulation ofmenstrual function, although Magnesium isinvolved in basal metabolism that changed over

calciuminorganic phosphorous

the course ofmenstrual cycle (5). These evidencessuggest possibly ovarian hormones influence Ca,Mg and Pi metabolism during the differentphases of menstrual cycle.

The purpose of this study is to evaluatechanges in serum Ca, Mg and Pi levels duringmenstrual cycle in healthy normallymenstruating women.

METHODS

Twenty five healthy medical studentvolunteers, 18-25 years of age, participated assubjects in this serial study. The subjects wereselected on the basis of normal and regualrmenstrual cycle (28±2 days cycle). The bloodsample was taken from each subjects duringtheir Menstrual, Follicular, Ovulatory and Lutealphases.

The determination of different phases andthe procedures of collection of blood during thosephases has been explained earlier (1). In brief,10 ml venous blood was drawn between 8.00 a.m.and 9.00 a.m. in each phase. Period of ovulation

*Corresponding Author

412 Pandya et al

was judged by daily basal oral temperaturerecordings. Estimation of serum Ca, Mg and Piwas carried out on the same day of collection bystandard methods :

Ca and Mg by Ethylene diamine tetra aceticacid titration (6).

Pi by Photometric method of Fisk andSubbarow (6).

Statistical analysis was done by paired 't'test. Level of significance was set at a P valueof <0.05.

RESULTS

Serum Ca, Mg and Pi levels during variousphases of menstrual cycle are summarised inTable I and represented graphically in Fig. 1.

Gradual increase in serum Ca level was seenfrom menstrual to follicular (P<0.001) and thento ovulatory phase (P<O.OOl)followed by lutealdecrease (P<O.Ol) as compared to menstrualphase.

Serum Mg level gradually decreases frommenstrual to ovulatory (P<O.OOl)phase only.Thereafter it rises to its maximum in lutealphase (P<O.OOl).

There is a cyclic variation in Pi level duringthe menstrual cycle. The highest level was seenduring menstrual phase (P<O.OOl)compared toall the three phases. During ovulation Pi levelincreased significantly (P<O.OOl)compared tofollicular phase. The Pi level is lowest (P<O.OOl)in luteal phase compared to all other phases ofthe menstrual cycle.

TABLE I: Shows mean (± S.D.) serum Ca, Mgand Pi levels during menstrual cycle.

Phases of men- Ca Mg Pistrual cycle mgllOO ml mg/100 ml mgllOO ml

Menstrual (M) 9.14±O.42 1.56±O.lO 5.10±O.48

Follicular (F) 9.66±O.49 1.46±O.O9 4.28±O.31

Ovulatory (0) 10.34±O.48 1.32±O.14 '4.63±O.37

Luteal (L) 8.80±O.34 1.63±1.17 3.84±O.34

MS/iee ml.

5'5 ~5·0

4'5

4'~

3'5

1,15

1i.·ss1,45

1-IS

1'25

U-o10,5

111-0

9'5

9·0

Indian J Physiol Pharmacol 1995; 39(4)

On comparison the values are significant with eachother at the level of P<O.OOI except for M vs L incase of Ca concentration (P<O.Ol).

INORGANIC PHOSPHOROUS

MAGNESIUM

CALCIUM

8'5 i iMENSTRUAL FOLLICULAR OVULPJ'ORY LUTEAL.

Fig. 1: Represents Ca, Mg and Pi level in serum duringvarious phases of menstrual cycle.

DISCUSSION

During past several years there has beenincreased interest in the study of relationshipbetween the essential minerals and ovarianhormone activity. Although the coordinatedsequence ofhormonal changes during the normalmenstrual cycle is well characterised, whethersimilar or parallel changes occur in thedistribution of selected minerals has not beenclearly established. Several studies have providedevidence for phase related changes in bloodconstituents during menstrual cycle (1, 7, 8).

Present study revealed distinct changesoccured in serum Ca, Mg and Pi level duringmenstrual cycle. Gradual but significant increasein serum Ca level was seen during menstrual,

Indian J Physial Pharmacal 1995; 39(4)

follicular and ovulatory phases compared to lutealphase. The results are analogous to the studiesthat report serum Ca is in highest concentrationduring ovulatory phase and in lowestconcentration during premenstrual phase (4)while some have stated slight variation duringmensus and intermensus though not significant(9).

It is reported that estrogen causes increasein parathyroid activity (7) which leads to markedacceleration of Ca uptake (10, 11) and decreaseof its elimination from pigeon's gut (2).Increments in blood Ca can result in increasedbone density in healthy women (12).From resultsit is evident that estrogen alone possibly causesincrease in blood Ca level during follicular andovulatory phase through parathyroid hormoneregulation. Withdrawal of estrogen causessignificant loss of bone Ca (13, 14).

Although estrogen increases during lutealphase, Ca level was found to be low. This cannotbe explained on the basis of estrogen levels andparathyroid activity alone, probably progesteronemight have more influence on it. Higher level ofprogesterone than estrogen during luteal phasemay interfere the activity of estrogen.Alternatively, because of priming effect ofestrogen is utilized to enhance the progesteroneactivity and may not involve in Ca uptake duringluteal phase.

There is controversy regarding serum Mgconcentration during menstrual cycle (7, 8). Ourstudy shows serum Mg level is maximum duringluteal phase, gradually decreases duringmenstrual and follicular phases and is lowestduring ovulatory phase. The cyclicvariation wasfound to be statistically significant.

Ovulatory decrease of serum Mg may berelated to preovulatory estrogen peak (15). Itcould be related to concurrent leutinisinghormone and follicle stimulating hormone peaksbut gonadotrophin effect on mineral retentionprobably requires an active gonad (16).

Changes in plasma Mg level could also berelated to changes in basal metabolic rate-BMR

Ca, Mg, Pi during Menstrual Cycle 413

(5). Increase in BMR and Oxygen consumptionduring luteal phase is associated with increasedcarbohydrate utilization. This carbohydrateutilization requires Mgion and oxidative enzymeswhich was found to be increased significantlyduring luteal phase (17, 18). Serum Mgconcentration has been possibly correlated withbasal body temparature (BBT) during ovulationand the luteal phase half cycle (19) but whetherMg increase is a cause or effect of increased heatcontent is difficult to decide. Although thehormone levels were not measured during thisstudy, it seems likely that progesterone isresponsible for rise in both BBT and serum Mg,which increased in parallel in a single day (18,19). Midcycle decline in Mg may be due toincreased parathyroid hormone or aldosterone,both of which increase before ovulation (7, 20).Progesterone is also known to act on centralnervous system to produce the luteal increase inbasal temperature (21). It is emphasized that theluteal phase is associated with increasedsympathetic activity (22). Thus increase in Mgmay cause decrease in Ca level by inhibiting orcompeting for common Ca reabsorptive sites inloop of Henle. Specific inhibition of Careabsorption by Mg increases urinary Caexcretion (23). Thus decline in serum Ca is adirect response to elevated serum Mg and itsaction on nephron.

Cyclic changes in Pi level were observed inthis study. The decrease in Pi level duringovulation could be on account of estrogen asindicated by earlier studies (24). Carvelhohas stated high production of estrogen leadsto decrease in serum Pi level (25). Thusinverse relation of Pi and estrogen level isseen. At present it is difficult to explainthe cause.

In conclusion, although the cyclic changesare noted in serum Ca, Mg and Pi levelduring the menstrual cycle, they were allfound to be within physiological limits. Thesechanges are probably brought about under theinfluence of cyclic variations of the ovarianhormones.

414 Pandya et al Indian J Physiol Pharmacol 1995; 39(4)

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