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Induced Lactation and Relactation (Including Nursing an Adopted Baby) and Cross-Nursing
Key Points
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Induced lactation is the process through which a nonpuerperal woman is stimulated to breastfeed an infant without a preceding pregnancy. Relactation is when a woman who has given birth but stopped breastfeeding or never initially breastfed is stimulated to lactate.
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Induced lactation and relactation are important processes for assisting women to nourish infants (their own or others) when circumstances have changed and there is an urgent need for ongoing nutrition and nurturing. These situations can arise in the early or late postpartum period, as a result of health or social situations for the mother, adoption, and emergencies or disasters that separate infants from their mothers.
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The recommendations for facilitating the processes of induced lactation or relactation have not been studied through rigorous clinical trials but constitute suggestions based on experience or empiric observation. There are a variety of resources, published and online, for assisting and supporting women in their efforts.
Breastfeeding has returned to be the preferred form of nourishment for the infant, and there has been an increased interest in induced lactation. Induced lactation is the process by which a nonpuerperal woman is stimulated to lactate—in other words, breastfeeding without pregnancy. Relactation is the process by which a woman who has given birth but did not initially breastfeed is stimulated to lactate. This may also apply to a mother who may have initially breastfed her infant, weaned the infant, and then chooses to reinstitute lactation. Relactation can also involve a woman who previously breastfed a biologic child, even years before, and now is adopting a newborn. There are no blinded controlled research studies about either induced lactation or relactation. There are occasional observation reports about successes in a small series of dyads. The process has not been confirmed by clinical trials. 1 Otherwise the literature is meager and predominantly in the animal research field.
Historical Perspective
Induced lactation and relactation are not new concepts but rather are well known to history and to other cultures. The motivation historically has been to provide nourishment for an infant whose mother has died in childbirth or is unable to nurse for some reason. A friend or relative would take on the care of the child and with it the responsibility to nourish the infant at the breast because no other alternatives were available.
Relactation has been used in times of disaster or epidemics to provide safe nutrition to weaned or motherless infants. Numerous historical accounts of induced lactation are recorded in the medical literature and reviewed in the writings of Brown. 2 Mead recorded the occurrence of relactation in her writings about New Guinea in 1935. 3 Other anthropologists have made similar observations in other preindustrialized societies of women who have not recently borne children and, after a few weeks of placing the suckling infant to the breast, produce milk adequate to nourish the infant. 4 Until recently, Western world literature reported the phenomenon as an anecdotal report as part of the discussion of aberrant lactation. In 1971, Cohen reported a patient who had been nursing an adopted child successfully for weeks when first seen in his pediatric office. 5
Today, the interest in induced lactation in the industrialized world stems from a desire on the part of adopting mothers to nurture an adopted child at the breast even though they were unable to carry the infant in utero. The interest in relactation comes from mothers of sick or premature infants who want to breastfeed their infants after the days and weeks of neonatal intensive care are over. These mothers, although postpartum, have not been lactating.
Induced Versus Inappropriate Lactation
The process of induced lactation is separate from galactorrhea, or inappropriate lactation, which has been described in the medical literature for more than 100 years. 6 Abnormal lactation has been observed in various circumstances in nulliparous and parous women and even in men. There are many eponyms for these conditions, usually based on the name of the physician who first described the syndrome, such as Chiari-Frommel and Ahumada-del Castillo.
Normally in the absence of suckling, lactation ceases 14 to 21 days after delivery. Milk flow that continues 3 to 6 months after abortion or any termination of pregnancy is termed abnormal or inappropriate lactation , or galactorrhea . Galactorrhea also refers to lactation in a woman 3 months after weaning or the secretion of milk in a nulliparous woman in association with hyperprolactinemia and amenorrhea. Although these cases are pathologic in nature and, therefore, different from the groups under discussion, it is noteworthy that some knowledge of the initiation and maintenance of lactation has been gained from the study of these syndromes. A nonpregnant woman who develops spontaneous lactation should be evaluated for hormonal disease. The most common cause is a prolactinoma of the pituitary. Spontaneous lactation should not be ignored. See Chapter 16 Breast Conditions in the Breastfeeding Mother for discussion of nipple discharge and hyperlactation.
Animal Studies
Information on the incidence of non-offspring nursing in 100 mammalian species has been assembled by Packer et al. 7 The incidence of non-offspring nursing is increased by captivity. It is more common in species with large litters (polytocous taxa) and differs from that which occurs with single young species (monotocous taxa). In the latter, it is more common for females to continue nursing after they have lost their own young. Among nondomesticated animals, spontaneous lactation has been observed repeatedly only in the dwarf mongoose ( Helogale parvula) .
Lactation has been induced for scientific and commercial purposes in nonpregnant and nonparturient animals by the continual systematic application of a mechanical milking apparatus to the mammary gland of the animal. 8 The response is produced through the release of a mammotropic hormone from the anterior pituitary gland. This effect is abolished if the pituitary stalk is transected. Ruminants respond to the addition of estrogen or estrogen-progesterone combinations, which facilitate mammary growth. Experiments in goats involved applying ointment containing estradiol benzoate to the udders of virgins, which resulted in development of the udder and milk yield almost comparable to that of normal postpartum animals. 9 It was subsequently shown, however, that a combination of estrogen-progesterone not only resulted in better milk yield, but histologically the lobuloalveolar growth was normal, whereas with estrogen alone growth was cystic and irregular. It was also demonstrated that ovariectomized goats could be stimulated to lactate with these two hormones, with resultant normal histology of the udder and good milk production. Initiation of regular milking had a significant impact on production of milk.
Because lactation can be stimulated when the ovaries have been removed but not when the pituitary stalk has been severed, this has significance for understanding some of the postpartum lactation failures in women. Again, in ruminants, growth hormone and thyroid hormone have been shown to increase milk yield, although prolactin does not. This suggests that prolactin is not deficient in ruminants. Because the motivation, goals, and physiologic problems may be slightly different, induced lactation and relactation in women are discussed separately.
Induced Lactation
When a mother chooses to nurse her adopted infant, the goal is usually to achieve a mother–infant relationship that also may have the benefit of some nutrition. In that perspective, success can be evaluated on the basis of whether an infant will suckle the breast and achieve some comfort and security from this opportunity and close relationship with the new mother. As has been well described by Avery, 10 this is nurturing with the emphasis on nurturing, not on “breastfeeding” or nutrition. A mother who is interested in inducing lactation to nurse an adopted infant may need to understand that she may never be able to sustain the infant completely by her milk alone without supplementation. Neither the physician nor the mother should be disappointed. The nurturing goal is still achieved. An adoptive mother induced lactation for premature twins who were exclusively breastfed by 2 months of age. The mother succeeded because of careful planning and support of the health care team. 11
Preparation of the Breast
Normally the breast is prepared by the proliferation of the ductal and alveolar system throughout pregnancy in anticipation of the time when lactation will begin, when the infant delivers and the placenta is removed. 12 Thus it is appropriate to assume that a period of similar preparation should take place in induced lactation. It has been suggested that a woman should begin systematically to express the breasts manually and stimulate the nipples for up to 2 months before the arrival of the infant, if time permits. A hand pump or other pumping devices can be used, but manual expression may work as well or better. Sometimes some secretion can be produced in this manner if it is carried out systematically on a uniform schedule throughout the day. The schedule should be practical, that is, include times when a mother could take a moment for this activity, such as morning and night plus any times she uses the bathroom or can conveniently handle her breasts.
Hormones and Medications
A more aggressive approach involves hormones and medications. During pregnancy, the breasts are prepared by the hormones generated by the pregnancy, estrogen, progesterone, and human placental lactogen (see Chapter 3, Fig. 3.3 ).
To mimic this environment, it has been suggested that starting a course of estrogen and progesterone would be appropriate, namely, prescribing oral contraceptive dosing that suppresses ovulation (such as Ortho-Novum). This dosing should be maintained without a pause as it would be during pregnancy. 13 Unfortunately, women who are adopting typically do not have 9 months to prepare, so priming the breasts with hormones may not be possible because the hormones need to be discontinued a month before anticipated lactation.
Concomitant with hormone therapy should be breast stimulation with systematic pumping with a good electric double pump. Timing should begin gradually, 5 minutes three times per day, then 10 minutes three times a day, increasing to a frequency every 4 hours. Pumping about the same time every day is helpful. It usually takes about a month before drops of milk appear. This is a good time to start domperidone (not available in the United States). 14 , 15 , 16 There have been concerns in women taking domperidone about cardiac mortality and prolonged QTc but no such infant mortality resulting from exposure through breast milk. The schedule adopted by Newman 17 in Canada is 10 mg three times per day, increasing during a month’s time to 20 mg four times per day. Newman 17 suggests using domperidone from the beginning. Without a placenta, the adoptive mother does not have “prolactin-inhibiting” hormone to block the breast from responding to the prolactin secreted because of the breast stimulation. Health care providers should be able to discuss the use of domperidone and participate in a discussion with the mother about the risks and benefits of its use in induced lactation or relactation. 18 , 19 When domperidone is initiated, milk should appear in increasing quantities. Many women have achieved success by pumping alone initially and then adding galactagogues.
In other cultures, in which lactation is induced as a survival tactic for the infant, no period of preparation is available. An infant is put to the adoptive mother’s breast and allowed to suckle. Emphasis has been placed on herbal teas as galactagogues and good nourishment for the mother, and the infant is also given prechewed food, gruel, or animal milk. Mead attributed much of the success of induced lactation to the ingestion of ample supplies of coconut milk by the new mother. 3 Coconuts are well known in herbal medicine; the oil pressed from ripe fruit is used for wound healing and inflammation reduction. 20 Adoption is not an easy process, and, in fact, it can be quite stressful to become an instant parent. In assisting such a mother, consideration should be given to the infant’s age, previous feeding experience, and any medical problems that may exist. Provision for additional nourishment during the process of establishing some milk secretion is most important. Onset of lactation varies from 1 to 6 weeks, averaging about 4 weeks after initiation of stimulation with the appearance of the first drops of milk. When the infant is actually nursing at the breast and being nourished by supplements, milk may appear as early as 1 to 2 weeks.
Some infants are easily confused by switching back and forth between breast and bottle because the sucking technique is slightly different. Other nourishment can be offered by dropper, by small medicine cup, or as solid foods. A unique system is available, however, for providing nourishment for the infant while suckling at the breast. It involves the use of a device to provide a source of nourishment while the infant suckles at the breast, thus stimulating production. It is further described later in this chapter and is called the Lact-Aid Nursing Trainer System (Lact-Aid International Inc., Athens, Tennessee) or Supplemental Nursing System (Medela Inc., McHenry, Illinois) ( Fig. 19.1 ).
Other Drug Schedules to Induce Lactation
As described in Chapter 3 , estrogen and progesterone stimulate the proliferation of the alveolar and ductal systems. These hormones work in association with an increase in prolactin production. Although the prolactin level is high during pregnancy, milk secretion is inhibited by the presence of the estrogen, progesterone, and placental lactogen, the prolactin-inhibiting hormone. After delivery has occurred and the placenta is removed, these hormone levels fall, and prolactin initiates milk production. Efforts to stimulate this hormonal response have had variable success and are not usually recommended because of the possible effect on an infant through the milk. Women taking oral contraceptives have been noted in some cases to have breast enlargement. In addition, although estrogen and progesterone may enhance proliferation, they may inhibit lactation per se, so they must be discontinued well before lactation is planned to begin.
The dosage of conjugated estrogens recommended by Waletzky and Herman is 2.5 mg twice per day for 14 days beginning on the fourth day of a regular menstrual cycle. 21 Giving 0.35 mg norethindrone once daily for the morning dose of estrogen prevents breakthrough bleeding. Medication is given for 2 weeks and is comparable in dosage to 2 weeks of oral contraceptives. This therapy may be accompanied by some side effects. The regimen should include direct efforts to stimulate lactation by pumping the breasts.
A report from Papua New Guinea, where inducing lactation is critical to adequate infant nutrition, recommends priming the breast tissue of nulliparous women or those who have not lactated with 50 mcg ethinyl estradiol three times per day for a week. 22 Medroxyprogesterone (Depo-Provera) has been used to initiate lactation in nonpuerperal women. A dose of 100 mg is given intramuscularly once, one week before stimulating the breast with massage and pumping. Galactagogues, such as metoclopramide, domperidone, or herbals, can be introduced. 23 (See Chapter 11 for discussion of some galactagogues.) This approach was reported in Papua New Guinea, and success was claimed in 24 of 27 women. 24 When relactation is the goal in women who have previously lactated, pumping and massaging alone are initiated.
Growth hormone and prolactin have considerable genetic similarity, as reflected in some overlap of function. 25 High concentrations of growth hormone can cause lobuloalveolar development and casein expression. Growth hormone may play a role in optimization of milk production during lactation and even an accessory role in the induction of lactogenesis. Both natural and recombinant human growth hormones are potent inductors of milk synthesis in pregnant and lactating rats. This effect is attributed to their effect on the prolactin receptor. 25
Oxytocin is a critical component in the milk-ejection reflex and may be helpful in the early initiation of ejection. Physiologically, stimulation of the nipple in the lactating woman results in the release of oxytocin by the hypothalamus, which then triggers the release of milk by stimulating the contraction of myoepithelial cells and the ejection of milk (see Chapter 3 ). The effect of intranasal administration of oxytocin on the let-down reflex in lactating women was well described by Newton and Egli. 26 (Oral administration by tablet is not as effective because oxytocin is destroyed in the stomach; therefore oral administration must be sublingual.) Oxytocin nasal spray has been used in cases of nonpuerperal lactation with some success in enhancing let-down but not necessarily altering the volume produced. The original oxytocin product, Syntonin, is no longer available, but a pharmacist by prescription can place the intravenous preparation in a dropper bottle or a nasal spray container. The intravenous preparation (10 units/mL) is one-quarter the strength of the old nasal spray (40 units/mL). Therefore the dose needs to be increased four-fold: 4 to 6 drops per dose in one naris and feed the infant or pump immediately. The dose can be repeated. Continued use of oxytocin for weeks has been associated with diminished effect or even suppression of lactation.
In a randomized, double-blind trial of oxytocin nasal spray in mothers expressing breast milk for preterm infants, there were only marginal differences in the pattern of early milk production. The use of oxytocin nasal spray did not significantly improve outcome. Most of the subjects thought they were receiving the real medicine, which demonstrates the power of the placebo effect. All of the mothers had been pregnant, and their breasts had responded to the pregnancy. 27 These data should not be extrapolated without further study to women who had never been pregnant.
The chief benefit of oxytocin is often to break the cycle of failure and instill a feeling of confidence once it has been demonstrated that some secretion can be produced.
Galactagogues
Galactagogues, a substance, product, or medication used to increase milk production, such as metoclopramide, domperidone, or herbals, can be introduced. 23 (See Chapter 11 for additional discussion of some galactagogues.) Chlorpromazine has been observed to act as a galactagogue as well as a tranquilizer when given to patients in large doses (200 mg to 1000 mg). The effect has been observed in both male and female patients in mental institutions. The drug has been reported to increase pituitary prolactin secretion several fold. It acts by the hypothalamus, probably by reducing levels of prolactin inhibitory factor (PIF). Using this information, women well motivated to lactate who have attempted induced lactation by suckling a normal infant have had the process enhanced by small doses of chlorpromazine.
In a program to induce lactation in refugee camps in India and in Vietnam, nonlactating women were given 25 to 100 mg of chlorpromazine three times per day for a week to 10 days while infants were initially put to breast. Brown 28 reports apparent enhancement of lactation with this treatment. Chlorpromazine has the added pharmacologic effect of acting as a tranquilizer. The program of management in these women was supportive in other ways and also included the usual herbal medicines associated with lactation in these Eastern cultures. There was no control group. 28 It is possible that the drug contributed to both the physiologic and the psychologic well-being of the women wanting to lactate. It has been suggested that the desire to lactate is a strong component of success because women whose breasts are frequently stimulated sexually do not begin to lactate.
Theophylline also can increase pituitary prolactin secretions. 29 Therefore both tea and coffee should enhance prolactin secretion and thus lactation. Excessive amounts may inhibit milk let-down, however. (See Tables 19.1 and 19.2 and for other agents that may affect induced lactation.)
Table 19.1
Pharmacologic Agents to Induce Lactation: Possibly Effective for Selected Indications
Modified from Brodribb W. ABM clinical protocol no. 9: use of galactogogues in initiating or augmenting maternal milk production, second revision 2018. Breastfeed Med . 2018;13(5):307–314. doi:10.1089/bfm.2018.29092.wjb .
| Domperidone | Fenugreek | Metoclopramide | Silymarin a | |
|---|---|---|---|---|
| Chemical class or properties | Dopamine antagonist | A commonly used spice; active constituents are trigonelline, 4-hydroxyisoleucine, and sotolon | Dopamine antagonist | Flavolignans (presumed active ingredient) |
| Level of evidence | I (one study); other studies have inadequate methodology or excessive dropout rates | II-3 (one study in lactating women—abstract only) | III (mixed results in low-quality studies; effect on overall rate of milk secretion is unclear) | II-I (one study in lactating women) |
| Suggested dosage | 10 mg orally three times per day in the Level I study; higher doses (20 mg orally TID) have been studied in this context | “3 capsules” orally (typically 580–610 mg), three to four times per day; strained tea, 1 cup, three times per day ({1/4} tsp of seeds steeped in 8 oz of water for 10 minutes) | 10 mg, orally, three to four times per day; doses of 30–45 mg/day were most effective | Micronized silymarin, 420 mg orally per day; anecdotal; strained tea (simmer 1 tsp of crushed seeds in 8 oz of water for 10 minutes), 2–3 cups/day |
| Length/duration of therapy | Started between 3 and 4 weeks postpartum and given for 14 days in the Level I study. In various other studies the range was considerable: Domperidone was started between 16 and 17 days postpartum and given for 2–14 days | 1 week | 7–14 days in various studies | Micronized silymarin was studied for 63 days |
| Herbal considerations | — | Need reliable source of standard preparation without contaminants | — | Need reliable source of standard preparation without contaminants |
| Effects on lactation | Increased rate of milk secretion for pump-dependent mothers of premature infants of younger than 31 weeks’ gestation in neonatal intensive care unit | Insufficient evidence; likely a significant placebo effect | Possibly increased rate of milk secretion; possible responders vs. nonresponders | Inconclusive |
| Untoward effects | Maternal: Dry mouth, headache (resolved with decreased dosage), and abdominal cramps. Although not reported in studies of lactation, cardiac arrhythmias resulting from prolonged QTc interval are a concern and are occasionally fatal. This may occur with either oral or intravenous administration and particularly with high doses, or concurrent use of drugs that inhibit domperidone’s metabolism (see Interactions, later). Neonatal: Very low levels in milk and no QTc prolongation in premature infants who had ingested breast milk of mothers taking domperidone | Generally well tolerated. Diarrhea (most common), unusual body odor similar to maple syrup, cross-allergy with Asteraceae/Compositae family (ragweed and related plants), peanuts, and Fabaceae family (e.g., chickpeas, soybeans, and green peas—possible anaphylaxis). Theoretically: Asthma, bleeding, dizziness, flatulence, hypoglycemia, loss of consciousness, skin rash, wheezing, but no reports in lactating women |
Reversible CNS effects with short-term use, including sedation, anxiety, depression/anxiety/agitation, motor restlessness, dystonic reactions, extrapyramidal symptoms. Rare reports of tardive dyskinesia (usually irreversible), causing the FDA to place a boxed warning on this drug | Generally well tolerated; occasional mild gastrointestinal side effects; cross-allergy with Asteraceae/Compositae family (ragweed and related plants—possible anaphylaxis) |
| Interactions | Increased blood levels of domperidone when combined with some substrates metabolized by CYP3A4 enzyme inhibitors (e.g., fluconazole, grapefruit juice, ketoconazole, macrolide antibiotics) | Hawthorne, hypoglycemics including insulin, antiplatelet drugs, aspirin, heparin, warfarin, feverfew, primrose oil, many other herbal agents | Monoamine oxidase inhibitors, tacrolimus, antihistamines, any drugs with CNS effects (including antidepressants) | Caution with CYP2C9 substrates—may increase levels of the drugs. Possible increased clearance of estrogens (decreased blood levels). Possible increased levels of statins |
| Comments | In the United States, the FDA has issued an advisory against the use of domperidone for lactating women. Do not advise exceeding maximum dosage; no increased efficacy but increased untoward effects. Licensed for use as a drug for gastrointestinal dismotility in some countries (but not in the United States), where for this indication in some regions it is accepted that if no response at the initial dose occurs, dose may be increased. Some areas use as drug of choice when prolactin stimulation is thought to be needed. However, there are no studies of the safety or efficacy of this practice in lactating women |
If patient develops diarrhea, reducing the dose is often helpful | Some studies suggest tapering the dose at the end of treatment | No prescription required |
CNS , Central nervous system; CYP , cytochrome P; FDA , US Food and Drug Administration.
a Silymarin (micronized silymarin) or S. marianum (milk thistle).
Table 19.2
Pharmacologic Agents to Induce Lactation: Controversial or Not Recommended, Although Possibly Effective
Modified from Brodribb W. ABM clinical protocol no. 9: use of galactogogues in initiating or augmenting maternal milk production, second revision 2018. Breastfeed Med . 2018;13(5):307–314. doi:10.1089/bfm.2018.29092.wjb .
| Human Growth Hormone | Sulpiride | Thyrotropin-Releasing Hormone | |
|---|---|---|---|
| Chemical class or properties | Protein-based polypeptide hormone: stimulates multiple growth, and anabolic and anticatabolic effects | Substituted benzamide (antipsychotic, antidepressant); antagonism of presynaptic inhibitory dopamine receptors | A tripeptide hormone that stimulates the release of TSH and prolactin by the anterior pituitary |
| Level of evidence | I, II | II-I (only two studies) | I |
| Suggested dosage | 0.2 international units/kg/day, given intramuscularly or subcutaneously | 50 mg orally two times per day; do not use higher doses because of sedation of mother and baby | 1 mg four times daily by nasal spray |
| Length/duration of therapy | 7 days, starting 8–18 weeks postpartum | 4-day course starting at 3 days postpartum; no evidence to use for a longer course of treatment | 10 days |
| Effects on lactation | Increased milk secretion in a selected population of normally lactating women with no feeding problems and with healthy, thriving infants between 8 and 18 weeks postpartum | Increased milk secretion in a selected population: Primiparous women with total yield of milk not exceeding 50 mL for the first 3 postpartum days | Increased milk secretion in selected population of primiparous women with insufficient milk supply at 5 days postpartum |
| Untoward effects | None observed in mothers or infants studied to date. Potentially: Joint swelling, joint pain, carpal tunnel syndrome, and an increased risk for diabetes or heart disease | Severe drowsiness; extrapyramidal effects same as for metoclopramide (above); weight gain | Elevated TSH and hyperthyroidism |
| Interactions | Other hormones, including contraceptives, insulin, cortisol, and others | Levodopa, other drugs with CNS effects | Other hormones, including contraceptives, insulin, cortisol, and others |
| Comments | Insufficient study; not practical—requires injection and is very expensive | Concern about untoward effects | Insufficient study, very expensive, no commercial product available |
CNS , Central nervous system; TSH , thyroid-stimulating hormone.
Because the role of prolactin is the initiation and maintenance of lactation, whereas oxytocin regulates the glandular emptying through the milk-ejection reflex, it is reasonable to speculate that enhancing prolactin release would be productive in inducing lactation. The exact activating mechanism of the neuronal reflex arc from breast to brain has not been deciphered. Secretion of prolactin appears to be influenced, if not controlled, by changes in hypothalamic dopamine turnover. Correspondingly, suckling has been observed to deplete dopamine stores.
Investigation of other drugs that are known to stimulate prolactin release has identified some possible therapeutic materials. Kramer reported that metoclopramide induces prolactin release regardless of the route of administration. 22 Prolactin levels are increased three to eight times normal levels within 5 minutes when a 10-mg dose of metoclopramide is given either intravenously or intramuscularly. The effect is achieved within an hour when metoclopramide is given orally. The effect persists for 8 hours. The suggested regimen is 10 mg of metoclopramide, three to four times per day for a week. 30 This is then gradually tapered (see Chapter 11 ).
Metoclopramide is also used in neonates with esophageal reflux. The side effects are irritability and diarrhea. Rarely, susceptible infants experience dystonic reactions, which have been described in adults. Metoclopramide has also been used in combination with chlorpromazine, 25 mg four times per day, in Papua New Guinea. 22 Metoclopramide has been used to enhance lactation, as well, especially among mothers of premature infants. 28
The regulation of prolactin secretion in humans has been studied to further the understanding of abnormal lactation and to provide information on the regulation of pituitary function of the brain. 31 It has been shown experimentally that the hypothalamus secretes PIF, which acts on the mammotropin-releasing cells of the pituitary to inhibit release of the hormone prolactin. The hypothalamus can also regulate prolactin secretion by a stimulatory mechanism, the secretion of thyrotropin-releasing hormone (TRH). When human volunteers (nonpregnant, nonlactating) are given infusions of TRH, increases in thyrotropin and prolactin are observed within minutes of injection, with values peaking in 20 minutes. The level of thyroid hormone in the volunteers initially influences the results. Patients with hypothyroidism have been observed to secrete excessive amounts of prolactin, whereas patients with hyperthyroidism are relatively insensitive to TRH. This may explain some of the variable results obtained with prolactin-stimulating drugs used to enhance lactation. Studies using TRH have been done on relactation but not on newly induced lactation. Thyroid activity has not been measured. Table 19.3 summarizes the influence of drugs on prolactin secretion. 29 ABM protocol no. 9 discusses the use of galactagogues and their effects and side effects (see Tables 19.1 and 19.2 ). 32
Table 19.3
Influence of Drugs on Prolactin Secretion
Modified from Vorherr H. Human lactation and breast feeding. In: Larson BL, ed. Lactation . New York, NY: Academic Press; 1978.
| Pharmacologic Agents | Plasma Prolactin Concentration | Mechanism of Drug Action |
|---|---|---|
| l -Dopa | Decrease | Increase in hypothalamic dopamine-catecholamine levels, leading to enhanced activity of PIF |
| Ergot alkaloids (ergocornine, ergocryptine) | Decrease | Direct inhibition of adenohypophyseal prolactin secretion; possible increase of hypothalamic PIF activity (continued PIF function) |
| TRH (pyroglutamyl histidyl-prolinamide) | Increase | Direct stimulation of adenohypophyseal lactotroph for increased prolactin secretion |
| Theophylline phenothiazines (chlorpromazine) | Increase | Decreases in hypothalamic dopamine-catecholamine levels, leading to diminution of PIF activity |
| Metoclopramide | Increase | Inhibition of hypothalamic PIF secretion through dopamine antagonism |
| Sulpiride | Increase | Increase in hypothalamic prolactin-releasing hormone |
| Growth hormone | Increase | Causes lobuloalveolar development and casein expression |
| Recombinant human growth hormones | Increase | Affects prolactin receptors |
PIF , Prolactin inhibitory factor; TRH , thyrotropin-releasing hormone.
Any pharmacologic regimen to stimulate milk production is most effective if it is initiated after the breast tissue has responded to mechanical stimulation because the hormones that act as the prolactin-stimulating compounds are thought by many to be ineffective in unprimed breast tissue. Jelliffe points out that the most important factor for continued production of milk is not drugs or hormones but “mulging.” 33 He explains that mulging (stimulation) is a word created by N. W. Pirie to mitigate the confusion between the words sucking and suckling . The word comes from the Latin mulgere , to milk. Suck , according to the dictionary, means to draw into the mouth by means of a partial vacuum created by action of the lips and the tongue. 34 Suckle , however, refers specifically to the breast and means “to give suck to,” as at the breast, or to take nourishment from the breast; thus, by definition, a bottle is not suckled.
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