Prolactin levels in nursing mothers D. L. BUNNER
E. F.
w. P.
VANDERLAAN VANDERLAAN*
La Jolla, California Plasma prolactin (hPRL) concentration was measured in four nursing mothers during 24 hour periods. Blood was collected via Indwelling catheters and sleep and nursing periods were recorded. Elevated hPRL levels and amenorrhea were seen for as long as 13 months postpartum in mothers whoSe infants nursed frequently. One mother, whose infant nursed less frequently, menstruated and had lower prolactin levels but continued to lactate. Plasma hPRL rose after nursing periods in nine of 18 instances at two months postpartum, but In only five of 27 instances at six months postpartum. Nighttime release hPRL was higher (five of six) in nursing mothers, just as In normal subjects (five of seven). Therefore it was concluded that prolactin levels In nursing mothers may remain elevated for over one year post partum If frequent nursing continues. Lactation may continue in spite of normal hPRL levels. A consistent rise in hPRL is not seen with nursing episodes occurring after two months post partum. Nursing mothers, like normal women, tend to have higher nighttime release of hPRL. (AM. J. 0BSTET. GYNECOL. 131': 250, 1978.)
only recently in man and much remains to be learned about its function and normal fluctuations. One area in which prolactin is certainly involved is in the production of normal lactation. Most reports thus far have suggested that suckling is promptly followed by a rise in prolactin leveJsH and that prolactin levels generally return to normal within a few months post partum. 4 It has also been postulated that a return to normal prolactin levels is associated with a resumption of normal menstrual cycling. 5 Most of these studies involved either single samples or brief studies before and after a single nursing episode. With such great hour-to-hour fluctuations in normal subjects,6· 7 single sample testing can be quite misleading. Also in brief studies of single nursing episodes it is quite possible that the procedure itself may be enough
120
PROLACTIN HAS BEEN MEASURED
From the Lutcher Brown Center for Diabetes and Endocrinology, Scripps Clinic and Research Foundation. Supported by Contract No. NOJ-CB-33881 and Grant No. CA-14025 awarded by the National Cancer Institute, and by GCRC Grant No. RR0083J from the Department of Health, Education, and Welfare. This is Publication No. 9 from the Lutcher Brown Center. Received for publication july 21, 1977. Accepted November 1, 1977. Reprint requests: Dr. David L. Bunner, Scripps Clinic and Research Foundation, 10666 N. Torrey Pines Rd .• La jolla, California 92037. *Olive H. Whittier Memorial Fund Investigator.
250
Soljttll
h~jKt
z-..•th tut,,rt••
l ..m.PniJatt••
l
Slllin.tl & lulh Puturt••
I... S.~ilt1 5~
0 •nth
b.
0800 1200 1800 2000 2400 0400
A
Puturltt~
b.
A
b.
ll
OBDD 120l 16811 2tll0 241111 8400
Time
Fig. 1. Clock time plotted against hPRL levels. Triangles indicate nursing periods. Solid bars on time axis indicate sleep periods. Circles indicate beginning and end of collection periods.
to evoke a prolactin response. Because of these potential pitfalls a small group of nursing mothers was studied over 24 hour periods during their normal routines, including nursing on demand. Materials and methods Patients. Four healthy mothers were selected for study. Two were studied at two and six months post 0002-9378/78/03131-0250$00.30/0 © 1978 The C. V. Mosby Co.
Voluli!le 131
Prolactin levels in nursing mothers 251
Numbt-r 3
Table I. Prolactin levels in nanograms per milliliter for normal women and nursing mothers Subject Nursing mothers: A B
c D
Normal, cycling:
Mo. post parium 2 6 2 6 13 SY2
E
,,F
v
Normal, birth control pill: H
Mean ::t S.E.M. * 24 hr. value 34.0 18.8 63.2 29.4 34.1 2.9
I
::t ::t ::t ::t ±
3.66 1.37 7.75 0.88 1.92 ± 0.30
5.7 ± 0.64 11.7 :!: 1.54 ""'A
,
A 1"\1
/."t:::!: U.!:!J
27.92 14.58 24.95 28.66 27.94 1.92
::t ::t ± ::t
4.22 0.89 2.12 1.18 ± 2.00 :t 0.21
' 1 \ '""(\
J
K
6.6 ± 0.34
5.90 ::t 0.30
Normal, meni>!Jausal, no estrogen:
%At + 67.5
::t 5.99 ::t 2.68 ± !3.40 ::t 1.01 ± 3.33 :t 0.61
+ 85.5 +191.7 + 3.8
+ 40.8
+147.0
--
456 ± 0.96 8.73:!: 0.42 1.4 1'\1
A "' -
E. F.
w. P.
VANDERLAAN VANDERLAAN*
La Jolla, California Plasma prolactin (hPRL) concentration was measured in four nursing mothers during 24 hour periods. Blood was collected via Indwelling catheters and sleep and nursing periods were recorded. Elevated hPRL levels and amenorrhea were seen for as long as 13 months postpartum in mothers whoSe infants nursed frequently. One mother, whose infant nursed less frequently, menstruated and had lower prolactin levels but continued to lactate. Plasma hPRL rose after nursing periods in nine of 18 instances at two months postpartum, but In only five of 27 instances at six months postpartum. Nighttime release hPRL was higher (five of six) in nursing mothers, just as In normal subjects (five of seven). Therefore it was concluded that prolactin levels In nursing mothers may remain elevated for over one year post partum If frequent nursing continues. Lactation may continue in spite of normal hPRL levels. A consistent rise in hPRL is not seen with nursing episodes occurring after two months post partum. Nursing mothers, like normal women, tend to have higher nighttime release of hPRL. (AM. J. 0BSTET. GYNECOL. 131': 250, 1978.)
only recently in man and much remains to be learned about its function and normal fluctuations. One area in which prolactin is certainly involved is in the production of normal lactation. Most reports thus far have suggested that suckling is promptly followed by a rise in prolactin leveJsH and that prolactin levels generally return to normal within a few months post partum. 4 It has also been postulated that a return to normal prolactin levels is associated with a resumption of normal menstrual cycling. 5 Most of these studies involved either single samples or brief studies before and after a single nursing episode. With such great hour-to-hour fluctuations in normal subjects,6· 7 single sample testing can be quite misleading. Also in brief studies of single nursing episodes it is quite possible that the procedure itself may be enough
120
PROLACTIN HAS BEEN MEASURED
From the Lutcher Brown Center for Diabetes and Endocrinology, Scripps Clinic and Research Foundation. Supported by Contract No. NOJ-CB-33881 and Grant No. CA-14025 awarded by the National Cancer Institute, and by GCRC Grant No. RR0083J from the Department of Health, Education, and Welfare. This is Publication No. 9 from the Lutcher Brown Center. Received for publication july 21, 1977. Accepted November 1, 1977. Reprint requests: Dr. David L. Bunner, Scripps Clinic and Research Foundation, 10666 N. Torrey Pines Rd .• La jolla, California 92037. *Olive H. Whittier Memorial Fund Investigator.
250
Soljttll
h~jKt
z-..•th tut,,rt••
l ..m.PniJatt••
l
Slllin.tl & lulh Puturt••
I... S.~ilt1 5~
0 •nth
b.
0800 1200 1800 2000 2400 0400
A
Puturltt~
b.
A
b.
ll
OBDD 120l 16811 2tll0 241111 8400
Time
Fig. 1. Clock time plotted against hPRL levels. Triangles indicate nursing periods. Solid bars on time axis indicate sleep periods. Circles indicate beginning and end of collection periods.
to evoke a prolactin response. Because of these potential pitfalls a small group of nursing mothers was studied over 24 hour periods during their normal routines, including nursing on demand. Materials and methods Patients. Four healthy mothers were selected for study. Two were studied at two and six months post 0002-9378/78/03131-0250$00.30/0 © 1978 The C. V. Mosby Co.
Voluli!le 131
Prolactin levels in nursing mothers 251
Numbt-r 3
Table I. Prolactin levels in nanograms per milliliter for normal women and nursing mothers Subject Nursing mothers: A B
c D
Normal, cycling:
Mo. post parium 2 6 2 6 13 SY2
E
,,F
v
Normal, birth control pill: H
Mean ::t S.E.M. * 24 hr. value 34.0 18.8 63.2 29.4 34.1 2.9
I
::t ::t ::t ::t ±
3.66 1.37 7.75 0.88 1.92 ± 0.30
5.7 ± 0.64 11.7 :!: 1.54 ""'A
,
A 1"\1
/."t:::!: U.!:!J
27.92 14.58 24.95 28.66 27.94 1.92
::t ::t ± ::t
4.22 0.89 2.12 1.18 ± 2.00 :t 0.21
' 1 \ '""(\
J
K
6.6 ± 0.34
5.90 ::t 0.30
Normal, meni>!Jausal, no estrogen:
%At + 67.5
::t 5.99 ::t 2.68 ± !3.40 ::t 1.01 ± 3.33 :t 0.61
+ 85.5 +191.7 + 3.8
+ 40.8
+147.0
--
456 ± 0.96 8.73:!: 0.42 1.4 1'\1
A "' -
