Neuroendocrinology 20: 43-46 (1976)
Effect of Suckling on Serum Follicle-Stimulating Hormone and Luteinizing Hormone in Nursing Women J. Soria, A. Z arate, E.S. C anales and H. V illalobos Department of Gynecologic Endocrinology, Hospital de Gineco-Obstetricia No. 1, Instituto Mexicano del Seguro Social, Mexico City
Key Words. FSH • LH • Suckling • Puerperal women Abstract. The effect of breast feeding on scrum FSH and LH concentrations was studied in 13 puerperal women. Despite the collateral increase in serum prolactin levels, nursing was not followed by significant changes in serum FSH or LH levels during a 30-min observation period. Our data indicate that nursing has no significant effect on pituitary FSH and LH release.
It has been stated that nursing elicits an increase in pituitary prolactin secretion associated with a simultaneous inhibition of gonadotropin release [M eites, 1966; M inaguchi and M eites, 1967; R eichlin, 1974], It has been explained that the mechanism of such an effect occurs through a neurogenic impulse and ultimately impinges upon the hypothalamus. The purpose of the present study was to determine whether breast feeding inhibited both pitui tary FSH and LH secretion during puerperium.
Materials and Methods
Received: July 30th, 1975; revised MS accepted: November 18th, 1975.
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13 volunteer puerperal lactating women were studied weekly for 4 weeks; a total of 88 samples were taken for FSH, and 46 for LH. Serum assays were performed on venous blood collected between 8 and 9 a.m., before breast feeding, and after 30 min of nursing. Serum LH and FSH concentrations were measured in duplicate by a double antibody radioimmunoassay [M idgley, 1966, 1967]; the highly purified reference preparation LER907 was used for iodination and dose interpolation. For intraassay error, the coefficient
44
Soria /Z árate/C anales/V illalobos SERUM
FSH
AND LH B E F O R E AND A F T E R
S UC K L I NG IN P UE RP E RA L WOMEN FSH log / m l )
Fig. 1. Comparison of maximum A FSH and maximum A LH following breast feeding in puerperal women. The darkened areas represent the undetectable range.
P R O L A C T I N L E V E L S t M E A N ± S E ) B E F O R E AND A F T E R SUCKLING
IN EIGHT L ACT AT ING
WOMEN
Fig. 2. Serum prolactin response to suckling during lactation.
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hPRL (ng / ml)
Suckling, FSH and LH in Nursing Women
45
of variation was 10% for LH and 7% for FSH. In this laboratory 1 ng of LER-907 is equivalent by radioimmunoassay to 0.02 n IU of LH and 0.06 /i 1U of FSH. Serum PRL was measured by the radioimmunoassay previously reported [H wang et al., 1971], utilizing highly purified hPRL. The reproducibility was satisfactory with intraassay and interassay variations of 8 and 15%, respectively. Student’s paired and unpaired /-tests were used to determine statistical significance.
Results The effect of breast feeding on the concentrations of FSH and LH is illustrated in figure 1. In most instances, serum FSH levels remained constant after suckling. A decrease in FSH levels was observed in 8 cases, and an increase in 6. Serum LH levels were not determined in the 1st week post partum because of the cross reactivity with chorionic gonadotropin. There after, serum LH levels remained the same after nursing, except for 3 instances in which the LH concentration increased with breast feeding. Serum prolactin levels increased during nursing in each case. This increase correlated with the time elapsed since delivery, as shown in figure 2.
Discussion
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The neurogenic-hormonal response to suckling includes the release of pituitary prolactin and, as is also assumed, the simultaneous inhibition of gonadotropin release [M eites, 1966; M inaguchi and M eites, 1967]. On the basis of clinical observations of ovarian function inhibition in the nursing mother, it has been proposed that inhibition of the release of FSH- and LHreleasing hormones results from a suckling-induced reflex. It is also believed that suckling-induced gonadotropin inhibition is due to a suckling-induced prolactin secretion that acts through short-loop feedback effects on the hypo thalamus. Present data provide no evidence for this theory. On the contrary, our results support the view that pituitary gonadotropin secretion is not inhibited by suckling and is able to respond to LH-RH administration during puerperium despite the presence of hyperprolactinemia [C anales et al., 1974; N akano et al., 1974]. Thus the most likely mechanism involved in the anovu latory state during puerperium is the ovarian refraction into gonadotropins [ZArate et al., 1972, 1974; R olland et al., 1975], because basal pituitary FSH and LH secretions are not inhibited after the 1st week post partum and suckling does not suppress gonadotropin release.
46
Soria /Z árate/C anales/V illalobos
Acknowledgments The reagents for radioimmunoassay of LH, FSH, and PRL were generously supplied through the National Pituitary Agency of the N1H, by Dr. L.E. R eichert of Atlanta.
References C anales, E.S.; Z arate, A.; G arrido, J.; L eón, C ; Soria, J., and Schally, A.V.: Study
on the recovery of pituitary FSH function during puerperium using synthetic LRH. J. clin. Endocr. Metab. 38: 1140-1142 (1974). H wang , P .: G uyda, H., and F riesen, H.: A radioimmunoassay for human prolactin. Proc. natn. Acad. Sci. USA 68: 1902-1906 (1971). M eites, J.: Control of mammary growth and lactation; in M artini and G anong Neuro endocrinology, vol. 1, pp. 669-707 (Academic Press, New York 1966). M idgley, A.R., j r .: Radioimmunoassay: a method for human chorionic gonadotropin and human luteinizing hormone. Endocrinology 79: 10-18 (1966). M idgley, A.R., jr .: Radioimmunoassay for human follicle-stimulating hormone. J. clin. Endocr. 27: 295-299 (1967). M inaguchi, H. and M eites, J.: Effect of suckling on hypothalamic LH-relcasing factor and prolactin inhibiting factor, and on pituitary LH and prolactin. Endocrinology 80: 603-607 (1967). N akano, R.; K ayashima, F.; M ori, A.; Kotsuji, F.; H ashiba, N., and Tojo, S.: Gonado tropin response to luteinizing hormone releasing factor (LRF) in puerperal women. Acta obstet. gynec. scand. 53: 303-307 (1974). R eichlin , S .: Neuroendocrinology; in W illiams Textbook of endocrinology, 5th ed., pp. 800-801 (W. B. Saunders Co., Philadelphia 1974). R olland, R . ; L equin, R. M .; Schellekens, L. A., and de Jong , F. H . : The role of prolactin in the restoration of ovarian function production during the early post-partum period in the human female. I.A. Study during physiological lactation. Clin. Endocr. 4: 15-25 (1975). Z árate, A.; C anales, E.S.; Soria , J.; León, C .; G arrido, J., and F onseca, E.: Refrac tory postpartum ovarian response to gonadal stimulation in nonlactating women. Obstet. Gynec., N.Y. 44: 819-822 (1974). Z arate, A.; C anales, E.S.; Soria , J.; Ruiz, F., and M acG regor, C : Ovarian refrac toriness during lactation in women: effect of gonadotropin stimulation. Am. J. Obstet. Gynec. 112: 1130-1132(1972).
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A. Z arate, Department of Gynecologic Endocrinology, Hospital de Gineco-Obstetricia No. 1, Gabriel Mancera 222, Mexico 12, D.F. (Mexico)
Effect of Suckling on Serum Follicle-Stimulating Hormone and Luteinizing Hormone in Nursing Women J. Soria, A. Z arate, E.S. C anales and H. V illalobos Department of Gynecologic Endocrinology, Hospital de Gineco-Obstetricia No. 1, Instituto Mexicano del Seguro Social, Mexico City
Key Words. FSH • LH • Suckling • Puerperal women Abstract. The effect of breast feeding on scrum FSH and LH concentrations was studied in 13 puerperal women. Despite the collateral increase in serum prolactin levels, nursing was not followed by significant changes in serum FSH or LH levels during a 30-min observation period. Our data indicate that nursing has no significant effect on pituitary FSH and LH release.
It has been stated that nursing elicits an increase in pituitary prolactin secretion associated with a simultaneous inhibition of gonadotropin release [M eites, 1966; M inaguchi and M eites, 1967; R eichlin, 1974], It has been explained that the mechanism of such an effect occurs through a neurogenic impulse and ultimately impinges upon the hypothalamus. The purpose of the present study was to determine whether breast feeding inhibited both pitui tary FSH and LH secretion during puerperium.
Materials and Methods
Received: July 30th, 1975; revised MS accepted: November 18th, 1975.
Downloaded by: King's College London 137.73.144.138 - 1/16/2019 3:10:19 AM
13 volunteer puerperal lactating women were studied weekly for 4 weeks; a total of 88 samples were taken for FSH, and 46 for LH. Serum assays were performed on venous blood collected between 8 and 9 a.m., before breast feeding, and after 30 min of nursing. Serum LH and FSH concentrations were measured in duplicate by a double antibody radioimmunoassay [M idgley, 1966, 1967]; the highly purified reference preparation LER907 was used for iodination and dose interpolation. For intraassay error, the coefficient
44
Soria /Z árate/C anales/V illalobos SERUM
FSH
AND LH B E F O R E AND A F T E R
S UC K L I NG IN P UE RP E RA L WOMEN FSH log / m l )
Fig. 1. Comparison of maximum A FSH and maximum A LH following breast feeding in puerperal women. The darkened areas represent the undetectable range.
P R O L A C T I N L E V E L S t M E A N ± S E ) B E F O R E AND A F T E R SUCKLING
IN EIGHT L ACT AT ING
WOMEN
Fig. 2. Serum prolactin response to suckling during lactation.
Downloaded by: King's College London 137.73.144.138 - 1/16/2019 3:10:19 AM
hPRL (ng / ml)
Suckling, FSH and LH in Nursing Women
45
of variation was 10% for LH and 7% for FSH. In this laboratory 1 ng of LER-907 is equivalent by radioimmunoassay to 0.02 n IU of LH and 0.06 /i 1U of FSH. Serum PRL was measured by the radioimmunoassay previously reported [H wang et al., 1971], utilizing highly purified hPRL. The reproducibility was satisfactory with intraassay and interassay variations of 8 and 15%, respectively. Student’s paired and unpaired /-tests were used to determine statistical significance.
Results The effect of breast feeding on the concentrations of FSH and LH is illustrated in figure 1. In most instances, serum FSH levels remained constant after suckling. A decrease in FSH levels was observed in 8 cases, and an increase in 6. Serum LH levels were not determined in the 1st week post partum because of the cross reactivity with chorionic gonadotropin. There after, serum LH levels remained the same after nursing, except for 3 instances in which the LH concentration increased with breast feeding. Serum prolactin levels increased during nursing in each case. This increase correlated with the time elapsed since delivery, as shown in figure 2.
Discussion
Downloaded by: King's College London 137.73.144.138 - 1/16/2019 3:10:19 AM
The neurogenic-hormonal response to suckling includes the release of pituitary prolactin and, as is also assumed, the simultaneous inhibition of gonadotropin release [M eites, 1966; M inaguchi and M eites, 1967]. On the basis of clinical observations of ovarian function inhibition in the nursing mother, it has been proposed that inhibition of the release of FSH- and LHreleasing hormones results from a suckling-induced reflex. It is also believed that suckling-induced gonadotropin inhibition is due to a suckling-induced prolactin secretion that acts through short-loop feedback effects on the hypo thalamus. Present data provide no evidence for this theory. On the contrary, our results support the view that pituitary gonadotropin secretion is not inhibited by suckling and is able to respond to LH-RH administration during puerperium despite the presence of hyperprolactinemia [C anales et al., 1974; N akano et al., 1974]. Thus the most likely mechanism involved in the anovu latory state during puerperium is the ovarian refraction into gonadotropins [ZArate et al., 1972, 1974; R olland et al., 1975], because basal pituitary FSH and LH secretions are not inhibited after the 1st week post partum and suckling does not suppress gonadotropin release.
46
Soria /Z árate/C anales/V illalobos
Acknowledgments The reagents for radioimmunoassay of LH, FSH, and PRL were generously supplied through the National Pituitary Agency of the N1H, by Dr. L.E. R eichert of Atlanta.
References C anales, E.S.; Z arate, A.; G arrido, J.; L eón, C ; Soria, J., and Schally, A.V.: Study
on the recovery of pituitary FSH function during puerperium using synthetic LRH. J. clin. Endocr. Metab. 38: 1140-1142 (1974). H wang , P .: G uyda, H., and F riesen, H.: A radioimmunoassay for human prolactin. Proc. natn. Acad. Sci. USA 68: 1902-1906 (1971). M eites, J.: Control of mammary growth and lactation; in M artini and G anong Neuro endocrinology, vol. 1, pp. 669-707 (Academic Press, New York 1966). M idgley, A.R., j r .: Radioimmunoassay: a method for human chorionic gonadotropin and human luteinizing hormone. Endocrinology 79: 10-18 (1966). M idgley, A.R., jr .: Radioimmunoassay for human follicle-stimulating hormone. J. clin. Endocr. 27: 295-299 (1967). M inaguchi, H. and M eites, J.: Effect of suckling on hypothalamic LH-relcasing factor and prolactin inhibiting factor, and on pituitary LH and prolactin. Endocrinology 80: 603-607 (1967). N akano, R.; K ayashima, F.; M ori, A.; Kotsuji, F.; H ashiba, N., and Tojo, S.: Gonado tropin response to luteinizing hormone releasing factor (LRF) in puerperal women. Acta obstet. gynec. scand. 53: 303-307 (1974). R eichlin , S .: Neuroendocrinology; in W illiams Textbook of endocrinology, 5th ed., pp. 800-801 (W. B. Saunders Co., Philadelphia 1974). R olland, R . ; L equin, R. M .; Schellekens, L. A., and de Jong , F. H . : The role of prolactin in the restoration of ovarian function production during the early post-partum period in the human female. I.A. Study during physiological lactation. Clin. Endocr. 4: 15-25 (1975). Z árate, A.; C anales, E.S.; Soria , J.; León, C .; G arrido, J., and F onseca, E.: Refrac tory postpartum ovarian response to gonadal stimulation in nonlactating women. Obstet. Gynec., N.Y. 44: 819-822 (1974). Z arate, A.; C anales, E.S.; Soria , J.; Ruiz, F., and M acG regor, C : Ovarian refrac toriness during lactation in women: effect of gonadotropin stimulation. Am. J. Obstet. Gynec. 112: 1130-1132(1972).
Downloaded by: King's College London 137.73.144.138 - 1/16/2019 3:10:19 AM
A. Z arate, Department of Gynecologic Endocrinology, Hospital de Gineco-Obstetricia No. 1, Gabriel Mancera 222, Mexico 12, D.F. (Mexico)
