Isolated prolactin deficiency: a case report

Isolated anterior pituitary dysfunction in adulthood

Hypopituitarism is defined as a complete or partial deficiency in one or more pituitary hormones. Anterior hypopituitarism includes secondary adrenal insufficiency, central hypothyroidism, hypogonadotropic hypogonadism, growth hormone deficiency and prolactin deficiency. Patients with hypopituitarism suffer from an increased disability and sick days, resulting in lower health status, higher cost of care and an increased mortality. In particular during adulthood, isolated pituitary deficits are not an uncommon finding; their clinical picture is represented by vague symptoms and unclear signs, which can be difficult to properly diagnose. This often becomes a challenge for the physician. Aim of this narrative review is to analyse, for each anterior pituitary deficit, the main related etiologies, the characteristic signs and symptoms, how to properly diagnose them (suggesting an easy and reproducible step-based approach), and eventually the treatment. In adulthood, the vast majority of isolated pituitary deficits are due to pituitary tumours, head trauma, pituitary surgery and brain radiotherapy. Immune-related dysfunctions represent a growing cause of isolated pituitary deficiencies, above all secondary to use of oncological drugs such as immune checkpoint inhibitors. The diagnosis of isolated pituitary deficiencies should be based on baseline hormonal assessments and/or dynamic tests. Establishing a proper diagnosis can be quite challenging: in fact, even if the diagnostic methods are becoming increasingly refined, a considerable proportion of isolated pituitary deficits still remains without a certain cause. While isolated ACTH and TSH deficiencies always require a prompt replacement treatment, gonadal replacement therapy requires a benefit-risk evaluation based on the presence of comorbidities, age and gender of the patient; finally, the need of growth hormone replacement therapies is still a matter of debate. On the other side, prolactin replacement therapy is still not available. In conclusion, our purpose is to offer a broad evaluation from causes to therapies of isolated anterior pituitary deficits in adulthood. This review will also include the evaluation of uncommon symptoms and main etiologies, the elements of suspicion of a genetic cause and protocols for diagnosis, follow-up and treatment.

PRL Mutation Causing Alactogenesis: Insights Into Prolactin Structure and Function Relationships

CONTEXT

Isolated prolactin deficiency is a rare disorder manifesting as absence of puerperal lactation. We identified a 2-generation family with 3 women experiencing alactogenesis.

OBJECTIVE

We hypothesized a heterozygous genetic mutation.

METHODS

This was a family-based study. Two generations of women (proband, sister, and niece) with puerperal alactogenesis and one control were studied. Prolactin levels in the 3 women ranged from 0.618 to 1.4 ng/mL (range, 2.8-29.2 ng/mL). All the women had regular menstrual cycles during their reproductive years. The niece required fertility treatment to become pregnant and the proband and sister underwent menopause before age 45 years. Prolactin gene (PRL) exons 1 to 5 were sequenced. We sought a heterozygous, deleterious gene variant with functional consequences.

RESULTS

We identified a heterozygous mutation (c.658C > T) changing CGA to TGA (p.Arg220Ter) in exon 5 of the prolactin gene. Transfection of PRL containing the stop gain mutation resulted in similar intracellular prolactin levels compared to PRL wild type, but little detectable immunoactive or bioactive prolactin in conditioned medium. Prolactin secretion was also impaired by a PRL stop gain mutation deleting both of the terminal cysteine amino acids (c.652A > T; p.Lys218Ter).

CONCLUSION

This is the first report of a PRL mutation causing familial prolactin deficiency and alactogenesis. The loss of the terminal cysteine resulted in failure of prolactin secretion. Secretion was not rescued by deleting the penultimate cysteine, with which it forms a disulfide bond. These data suggest that the PRL C terminal is critical for protein secretion.

UNDERSTANDING PROLACTIN REGULATION AND DETERMINING THE EFFICACY OF CABERGOLINE AND DOMPERIDONE TO MITIGATE PROLACTIN-ASSOCIATED OVARIAN CYCLE PROBLEMS IN ZOO AFRICAN ELEPHANTS (LOXODONTA AFRICANA )

Perturbations in serum prolactin secretion, both over- and underproduction, are observed in zoo African elephants (Loxodonta africana) that exhibit abnormal ovarian cycles. Similar prolactin problems are associated with infertility in other species. Pituitary prolactin is held under constant inhibition by a hypothalamic-derived neurotransmitter, dopamine; thus, regulation by exogenous treatment with agonists or antagonists may be capable of reinitiating normal ovarian cycles. This study tested the efficacy of oral administration of cabergoline (agonist) and domperidone (antagonist) as possible treatments for hyperprolactinemia or chronic low prolactin, respectively. Hyperprolactinemic (overall mean prolactin, >30 ng/ml), acyclic elephants were administered oral cabergoline (2 mg, n = 4) or placebo (dextrose capsule, n = 4) twice weekly. Overall mean prolactin concentration decreased in treated females compared with controls (32.22 ± 14.75 vs 77.53 ± 0.96 ng/ml; P = 0.01). Interestingly, overall mean progestagen concentrations also increased slightly (P < 0.05) in treated females (0.15 ± 0.01 ng/ml) compared with controls (0.07 ± 0.01 ng/ml), but no reinitation of normal cyclic patterns was observed. Chronic low prolactin (overall mean prolactin, <10 ng/ml), acyclic females were orally administered domperidone (2 g/day, n = 4) or placebo (dextrose capsule, n = 4) for 4 wk, followed by 8 wk of no treatment (four cycles) to simulate the prolactin pattern observed in normal cycling elephants. Overall mean prolactin concentrations increased (P = 0.005) during domperidone treatment (21.77 ± 3.69 ng/ml) compared with controls (5.77 ± 0.46 ng/ml), but progestagen concentrations were unaltered. Prolactin regulation by dopamine was confirmed by expected responses to dopamine agonist and antagonist treatment. Although prolactin concentrations were successfully reduced by cabergoline, and domperidone initiated the expected cyclic prolactin pattern, neither treatment induced normal ovarian activity.

Genetic and Physiological Factors Affecting Human Milk Production and Composition

Human milk is considered the optimal nutrition for infants as it provides additional attributes other than nutritional support for the infant and contributes to the mother's health as well. Although breastfeeding is the most natural modality to feed infants, nowadays, many mothers complain about breastfeeding difficulties. In addition to environmental factors that may influence lactation outcomes including maternal nutrition status, partner's support, stress, and latching ability of the infant, intrinsic factors such as maternal genetics may also affect the quantitative production and qualitative content of human milk. These genetic factors, which may largely affect the infant's growth and development, as well as the mother's breastfeeding experience, are the subject of the present review. We specifically describe genetic variations that were shown to affect quantitative human milk supply and/or its qualitative content. We further discuss possible implications and methods for diagnosis as well as treatment modalities. Although cases of nutrient-deficient human milk are considered rare, in some ethnic groups, genetic variations that affect human milk content are more abundant, and they should receive greater attention for diagnosis and treatment when necessary. From a future perspective, early genetic diagnosis should be directed to target and treat breastfeeding difficulties in real time.

Prolactinoma through the female life cycle

Prolactinomas are the most common secretory pituitary adenoma. They typically occur in women in the 3rd-6th decade of life and rarely in the pediatric population or after menopause. Most women present with irregular menses and/or infertility. Dopamine (DA) agonists, used in their treatment, are safe during pregnancy, but in most cases are discontinued at conception with close monitoring for signs or symptoms of tumor growth. Breastfeeding is safe postpartum, provided there was no significant growth during pregnancy. Some women will experience normalization of prolactin levels postpartum. Menopause may also decrease prolactin levels and even those with macroprolactinomas may consider discontinuing their DA agonist with close follow-up. Prolactinomas may be associated with decreased quality of life scores in women, and play a role in bone health and cardiovascular risk factors. This review discusses the current literature and clinical understanding of prolactinomas throughout the entirety of the female life cycle.

Completely humanizing prolactin rescues infertility in prolactin knockout mice and leads to human prolactin expression in extrapituitary mouse tissues

A variety of fundamental differences have evolved in the physiology of the human and rodent prolactin (PRL) systems. The PRL gene in humans and other primates contains an alternative promoter, 5.8 kbp upstream of the pituitary transcription start site, which drives expression of PRL in "extrapituitary" tissues, where PRL is believed to exert local, or paracrine, actions. Several of these extrapituitary PRL tissues serve a reproductive function (eg, mammary gland, decidua, prostate, etc), consistent with the hypothesis that local PRL production may be involved in, and required for, normal reproductive physiology in primates. Rodent research models have generated significant findings regarding the role of PRL in reproduction. Specifically, disruption (knockout) of either the PRL gene or its receptor causes profound female reproductive defects at several levels (ovaries, preimplantation endometrium, mammary glands). However, the rodent PRL gene differs significantly from the human, most notably lacking the alternative promoter. Understanding of the physiological regulation and function of extrapituitary PRL has been limited by the absence of a readily accessible experimental model, because the rodent PRL gene does not contain the alternative promoter. To overcome these limitations, we have generated mice that have been "humanized" with regard to the structural gene and tissue expression of PRL. Here, we present the characterization of these animals, demonstrating that the human PRL transgene is responsive to known physiological regulators both in vitro and in vivo. More importantly, the expression of the human PRL transgene is able to rescue the reproductive defects observed in mouse PRL knockout (mPRL(-)) females, validating their usefulness in studying the function or regulation of this hormone in a manner that is relevant to human physiology.

Isolated prolactin deficiency associated with serum autoantibodies against prolactin-secreting cells

CONTEXT

Isolated prolactin (PRL) deficiency is a rare entity of unknown etiology manifesting as failure of puerperal lactogenesis.

OBJECTIVE

The aim of the study was to determine the cause of isolated PRL deficiency in an affected woman.

DESIGN AND SETTING

We examined genetic and autoimmune causes of isolated PRL deficiency at academic medical centers.

PATIENT

The patient was a 39-year-old woman with puerperal alactogenesis after two deliveries and undetectable PRL. The other pituitary axes, serum calcium levels, and cranial magnetic resonance imaging were normal.

INTERVENTION

Recombinant human PRL (r-hPRL) was administered to the patient.

MAIN OUTCOME MEASURES

We measured the sequencing of candidate genes and immunofluorescence analysis of autoantibodies directed against pituitary endocrine cells.

RESULTS

There were no rare sequence variants in the genes encoding for PRL, putative PRL-releasing peptide, putative PRL-releasing peptide receptor, or in other genes important for lactotroph lineage development (POU1F1, PROP1, LHX3, LHX4, HESX1, OTX2, and LSD1). The patient serum, on the contrary, contained autoantibodies that specifically recognized a subset of PRL-secreting cells but not PRL itself or any other pituitary cells or hormones. The mother was able to lactate fully after 17 days of treatment with r-hPRL 60 μg/kg every 12 hours, but alactogenesis resumed after treatment was completed.

CONCLUSIONS

These studies report a new autoimmune etiology for women with isolated PRL deficiency and puerperal alactogenesis.

Prolactin serum concentrations during aripiprazole treatment in youth

OBJECTIVE

This study aimed to: document the extent of the reduction of serum prolactin (PRL) levels induced by aripiprazole (ARI) treatment in children and adolescents, compare this effect by age group, and shed light on this phenomenon.

METHODS

PRL serum levels in unmedicated subjects were compared to those in subjects treated with aripiprazole to calculate the rate of subnormal PRL levels during aripiprazole treatment. Next, a literature search was performed to better understand the effects of dopaminergic drugs on PRL levels by age group.

RESULTS

Sixty percent of those treated with aripiprazole exhibited subnormal PRL serum levels versus 8% of unmedicated subjects. The rate of PRL subnormality in response to aripiprazole was half as frequent in adolescents and was minimal in adults. The drug-induced reduction of PRL serum levels became more prominent with increasing doses of aripiprazole and with an increased treatment duration.

CONCLUSIONS

With the increasing use of aripiprazole in the United States population, it is important that future research be conducted to explore the potential sequelae of subnormal PRL serum levels in children and adolescents.

Prolactin secretion patterns: basic mechanisms and clinical implications for reproduction

Prolactin (PRL) is one of the most versatile hormones in the mammalian body affecting reproductive, sexual, metabolic, immune, and other functions. It is therefore not surprising that the neural control of PRL secretion is complex, involving the coordinated actions of several hypothalamic nuclei. A plethora of experimental data exists on the hypothalamic control of hormone secretion under various physiological stimuli. There have been even mathematical models and computer studies published, which help to understand the complex hypothalamic–pituitary network. Nevertheless, the putative role of PRL for human reproduction still has to be clarified. Here, we review data on the underlying mechanisms controlling PRL secretion using both experimental and mathematical approaches. These investigations primarily focus on rhythmic secretion in rats during early pregnancy or pseudopregnancy, and they point to the important role of oxytocin as a crucial PRL-releasing factor. Recent data on human studies and their theoretical and clinical implications are reviewed as well. In particular, studies demonstrating a sustained PRL surge after sexual climax in males and females are presented, indicating possible implications for both sexual satiation and reproductive functions. Taking these data together, there is evidence for the hypothesis that the PRL surge induced by sexual activity, together with the altered PRL rhythmic pattern, is important for successful initialization of pregnancy not only in rodents but also possibly in humans. However, further investigations are needed to clarify such a role in humans.

Acquired prolactin deficiency in patients with disorders of the hypothalamic-pituitary axis

Acquired PRL deficiency occurs when the anterior pituitary is functionally destroyed, and it usually accompanies other pituitary hormone deficiencies. We retrospectively investigated in an outpatient endocrine clinic of a major tertiary medical center the prevalence and clinical characteristics of acquired PRL deficiency in patients with diseases of the hypothalamic-pituitary axis. The study included 100 consecutive patients, 61 men and 39 women, aged 4-79 yr at diagnosis. Patients were divided by PRL level to normal (>5 ng/ml), mild (3-5 ng/ml), and severe deficiency (<3 ng/ml). Twenty-seven patients (27%) had PRL deficiency, 13 mild deficiency and 14 severe deficiency. Patients with severe PRL deficiency tend to be younger at diagnosis (mean age, 37.5+/-21.8 yr) than patients with normal PRL (46+/-18.5 yr; ns). Underlying diseases including pituitary apoplexy, non-functioning pituitary adenoma, craniopharyngioma, and idiopathic hypogonadotropic hypogonadism were associated with PRL deficiency. The incidence of severe PRL deficiency rose with an increase in the number of other pituitary hormone deficits (ACTH, TSH, gonadotropin, vasopressin), from 0 in patients with no other deficits to 38% in patients with 4 deficits (p=0.006). Patients with severe deficiency had a mean of 3 hormone deficits compared to 1.8 in the other groups (p=0.006). PRL deficiency was significantly associated with TSH, ACTH and GH deficiency.

CONCLUSIONS

PRL deficiency is common in patients with hypothalamic-pituitary disorders, especially pituitary apoplexy and craniopharyngioma. Acquired severe PRL deficiency can be considered a marker for extensive pituitary damage and a more severe degree of hypopituitarism.

A case of prolactin deficiency with familial puerperal alactogenesis accompanying impaired ACTH secretion

We report here the case of a 34-year-old female with puerperal alactogenesis. Her menstrual cycle was regular and breast development normal. She had delivered a healthy boy but could not breast-feed after parturition. Endocrinological studies disclosed that the cause was a prolactin (PRL) deficiency. In addition, she showed accompanying impaired ACTH secretion that was believed to be triggered by encephalitis, although her plasma levels of GH, TSH, LH and FSH remained intact. Pituitary MRI showed no specific findings and anti-pituitary antibody tests were negative. Interestingly, both her mother and grandmother also reported puerperal alactogenesis. The sequences of all five exons of the PRL gene, including promoter region and transcription initiation point, were surveyed in order to examine for certain genetic disorders, but no mutations were identified. Although it cannot be definitively concluded that this PRL deficiency was not a genomic DNA disorder, in our case at least, her PRL gene was normal and, therefore, was not directly responsible for the patient's impaired PRL secretion. This evidence suggests that familial puerperal alactogenesis and PRL deficiency can be induced by other causes such as via disorders of unknown transcription factors or molecules that contribute to translation of PRL gene.

Prolactin in man: a tale of two promoters

The pituitary hormone prolactin (PRL) is best known for its role in the regulation of lactation. Recent evidence furthermore indicates PRL is required for normal reproduction in rodents. Here, we report on the insertion of two transposon-like DNA sequences in the human prolactin gene, which together function as an alternative promoter directing extrapituitary PRL expression. Indeed, the transposable elements contain transcription factor binding sites that have been shown to mediate PRL transcription in human uterine decidualised endometrial cells and lymphocytes. We hypothesize that the transposon insertion event has resulted in divergent (pituitary versus extrapituitary) expression of prolactin in primates, and in differential actions of pituitary versus extrapituitary prolactin in lactation versus pregnancy respectively. Importantly, the TE insertion might provide a context for some of the conflicting results obtained in studies of PRL function in mice and man.

Aspects of placental growth hormone physiology

Placental growth hormone (PGH) has been known for 20 years. Nevertheless, its physiology is far from understood. In this review, basal aspects of PGH physiology are summarised and put in relation to the highly homologous pituitary growth hormone (GH). During normal pregnancy, PGH progressively replaces GH and reach maximum serum concentrations in the third trimester. A close relationship to insulin-like growth factor (IGF)-I and -II levels is observed. Furthermore, PGH levels are positively associated to fetal growth. The potential importance of growth hormone receptors and binding protein for PGH effects is discussed. Finally, the review outlines current knowledge of PGH in pathological pregnancies.

Endocrinology of lactation

The endocrine control of lactation is one of the most complex physiologic mechanisms of human parturition. Mammogenesis, lactogenesis, galactopoiesis, and galactokinesis are all essential to assure proper lactation. Prolactin is the key hormone of lactation and seems to be the single most important galactopoietic hormone. Oxytocin, serotonin, opioids, histamine, substance P, and arginine-leucine modulate prolactin release by means of an autocrine/paracrine mechanism, whereas estrogen and progesterone hormones can act at the hypothalamic and adenohypophysial levels. Human placental lactogen and growth factors play an essential role to assure successful lactation during pregnancy. Oxytocin is the most powerful galactokinetic hormone.

Novel vertebrate genes and putative regulatory elements identified at kidney disease and NR2E1/fierce loci

Fierce (frc) mice are deleted for nuclear receptor 2e1 (Nr2e1), and exhibit cerebral hypoplasia, blindness, and extreme aggression. To characterize the Nr2e1 locus, which may also contain the mouse kidney disease (kd) allele, we compared sequence from human, mouse, and the puffer fish Fugu rubripes. We identified a novel gene, c222389, containing conserved elements in noncoding regions. We also discovered a novel vertebrate gene conserved across its length in prokaryotes and invertebrates. Based on a dramatic upregulation in lactating breast, we named this gene lactation elevated-1 (LACE1). Two separate 100-bp elements within the first NR2E1 intron were virtually identical between the three species, despite an estimated 450 million years of divergent evolution. These elements represent strong candidates for functional NR2E1 regulatory elements in vertebrates. A high degree of conservation across NR2E1 combined with a lack of interspersed repeats suggests that an array of regulatory elements embedded within the gene is required for proper gene expression.

Puerperal alactogenesis with normal prolactin dynamics: is prolactin resistance the cause?

OBJECTIVE

To determine the cause of puerperal alactogenesis in a young woman.

DESIGN

After proper clinical assessment, a definitive investigative protocol was followed to determine the cause of alactogenesis.

SETTING

Tertiary care medical center in Kashmir, India.

PATIENT(S)

A young married woman with three full-term deliveries, all characterized by puerperal alactogenesis.

INTERVENTION(S)

An investigative protocol to document prolactin reserve and mammography to demonstrate presence of normal breast tissue.

MAIN OUTCOME MEASURE(S)

Prolactin secretory reserve.

RESULT(S)

The patient had normal breast development and an adequate pituitary prolactin reserve.

CONCLUSION(S)

Prolactin resistance may have caused alactogenesis.

Prolactin gene expression and prolactin protein in premenopausal and postmenopausal human ovaries

OBJECTIVE

To investigate intraovarian prolactin and prolactin-receptor gene expression and to assess local prolactin synthesis with emphasis on possible differences between premenopausal and postmenopausal status.

DESIGN

The RNA extracted from human premenopausal and postmenopausal tissues was subjected to reverse transcription and polymerase chain reaction by using prolactin-specific intron- and exon-spanning primers. Prolactin-receptor expression was investigated accordingly. The amplified complementary DNA fragments were analyzed by gel electrophoresis and restriction enzyme mapping. Local prolactin hormone synthesis was verified by a time-resolved immunofluorometric assay based on our monoclonal antibodies.

RESULT(S)

Prolactin and prolactin-receptor gene expression was observed in all analyzed human ovaries (n = 18). Several other human tissue specimens, such as lung and kidney, served as negative control tissues. Significantly elevated concentrations of prolactin were detected in cytosolic extracts of premenopausal (n = 6; mean +/- SD; 20.6 +/- 3.3 ng/g tissue wet weight) versus postmenopausal (n = 6; 3.6 +/- 3.0 ng/g tissue wet weight) ovaries.

CONCLUSION(S)

The human ovary not only serves as a target for endocrine prolactin action but also as a site of local prolactin hormone production. In agreement with previous reports on extrapituitary sources of prolactin, we consider prolactin as a hormone as well as an autocrine or paracrine growth or regulatory factor. Significantly increased concentrations of prolactin in premenopausal ovarian tissue verifies its role in human reproduction.