Increased body weight associated with prolactin secreting pituitary adenomas: weight loss with normalization of prolactin levels

Prolactin's mediative role in male parenting in parentally experienced marmosets (Callithrix jacchus)

Prolactin has been implicated in promoting paternal care behaviors but little evidence of causality has been found to date except for birds and fish. This study was designed to examine the possible causal relationships between prolactin and male parenting behaviors, reproductive hormones, and physical changes in cooperatively breeding common marmosets, Callithrix jacchus. Fifteen parentally experienced fathers were studied over three consecutive infant care periods during two weeks prior and three weeks following their mates' parturition under three-treatment conditions: normal control pregnancy, decreased prolactin and elevated prolactin. The treatments significantly altered the serum prolactin levels in the fathers. Using three methods of determining a father's level of parental care: infant carrying, family effort and responsiveness to infant stimulus tests, we found that only the male response to infant stimuli was altered by the hormone treatments. Lowering prolactin significantly reduced male responsiveness to infant stimuli but elevating prolactin showed the same effect. Hormonal sampling indicated that testosterone levels showed an inverse relationship to prolactin levels during a normal peripartum period and prolactin treatment reduced this relationship. Prepartum estradiol levels were significantly elevated during the lowered prolactin treatment and estradiol was significantly lowered postpartum with the elevated prolactin treatment. Father's weight decreased significantly by the third week of infant care during the normal treatment. Males in the elevated prolactin treatment lost little or no weight from prepartum while in the lowered prolactin treatment showed the most weight loss. The present findings did not distinguish a direct causal relationship of prolactin on behavior in experienced fathers but did find an interaction with other hormones and weight gain.

Hormonal control of aging in rodents: the somatotropic axis

There is a growing body of literature focusing on the somatotropic axis and regulation of aging and longevity. Many of these reports derive data from multiple endocrine mutants, those that exhibit both elevated growth hormone (GH) and insulin-like growth factor I (IGF-1) or deficiencies in one or both of these hormones. In general, both spontaneous and genetically engineered GH and IGF-1 deficiencies have lead to small body size, delayed development of sexual maturation and age-related pathology, and life span extension. In contrast, characteristics of high circulating GH included larger body sizes, early puberty and reproductive senescence, increased cancer incidence and reduced life span when compared to wild-type animals with normal plasma hormone concentrations. This information, along with that found in multiple other species, implicates this anabolic pathway as the major regulator of longevity in animals.

Evaluation of insulin sensitivity in hyperprolactinemic subjects by euglycemic hyperinsulinemic clamp technique

The background and aim of the study is to evaluate insulin sensitivity in hyperprolactinemic subjects via euglycemic hyperinsulinemic clamp technique. Sixteen hyperprolactinemic subjects and 12 healthy subjects were included in the study. HOMA-B and HOMA-IR values of groups were calculated. Euglycemic hyperinsulinemic clamp technique was performed in both groups, and the M value of the groups was defined. Mann-Whitney U and chi-square tests were used in statistical analysis. Basal insulin level of hyperprolactinemic patients were higher than the control group (6.85 +/- 4.68; 3.66 +/- 0.88 microU/ml respectively; P < 0.05). Mean HOMA-IR and HOMA-B values of patients were higher than control group (1.49 +/- 1.30; 0.78 +/- 0.27 respectively; P = 0.02 and 136.28 +/- 72.53; 64.77 +/- 23.31, respectively, P < 0.001). M values of the patients were statistically lower than the control group (5.64 +/- 2.36; 7.05 +/- 1.62 kg/mg/min respectively; P < 0.05). (1) Hyperprolactinemic patients were more insulin resistant than control subjects. (2) Insulin resistance in hyperprolactinemic patients is not associated with obesity or anthropometric parameters such as fat content, waist circumference and BMI.

The effects of hyperprolactinemia on bone and fat

Many patients with prolactin secreting pituitary tumors have decreased bone mineral. The bone loss is associated with an increase in bone resorption and is secondary to prolactin-induced hypogonadism. In both sexes trabecular bone in the spine and hip is more affected than cortical bone in the distal radius. Normalization of prolactin and restoration of gonadal function increases bone density but is not associated with normalization of bone mass. It is not known whether the bone loss in hyperprolactinemic subjects represents a failure to achieve peak bone mass or is due to accelerated bone loss. Despite low bone density hyperprolactinemic subjects do not demonstrate increased fractures. The association between prolactin, weight gain and obesity suggests that prolactin may also be a modulator of body composition and body weight. It is not known whether hyperprolactinemia associated weight gain is due to stimulation of lipogenesis or due to disruption of central nervous system dopaminergic tone. Hyperprolactinemia is also associated with insulin resistance and endothelial dysfunction which may improve after normalization of prolactin. The clinical significance of these findings and the precise role of prolactin in regulation of weight and metabolism remain to be elucidated.

Body fat in men with prolactinoma

OBJECTIVE

(a) To evaluate body fat in men with prolactinoma and healthy controls, using whole body dual energy x-ray absorptiometry (DXA), and (b) to correlate DXA results with anthropometry and clinical aspects of male prolactinomas.

MATERIAL AND METHODS

A cross-sectional study was performed in two University referral centers. Eleven newly-diagnosed men with prolactinoma and 9 with normal PRL levels due to dopamine agonist treatment were submitted to DXA and blood analysis (PRL, testosterone, dihydrotestosterone, estradiol, and SHBG) by the time of their clinical evaluation. They were compared with 14 control men of similar age and body mass index distribution.

RESULTS

Newly-diagnosed men with prolactinoma had higher fat percentage in the arms and the total body, when compared with patients treated with dopamine agonists and controls. The former group also presented higher fat percentage in the legs than the controls. Truncal fat percentage of the newly-diagnosed patients was lower than the dopamine agonist treated group. The 3 groups had similar android and gynoid fat contents. Fat percentage of the 6 sites correlated with PRL, testosterone, and dihydrotestosterone levels.

CONCLUSION

Newly-diagnosed men with prolactinomas had higher body fat content. Body fat was linked to disease control, especially to the PRL and androgen levels. Consequently, adequate control of hyperprolactinemia should be pursued in order to reduce the risk of obesity and its metabolic complications in men with prolactinoma.

Prolactin and insulin ultradian secretion and adipose tissue lipoprotein lipase expression in severely obese women after bariatric surgery

BACKGROUND

Hyperprolactinemia is associated with obesity. Furthermore, in human adipose tissue cultured in vitro, prolactin (PRL) inhibited lipoprotein lipase (LPL) activity via functional PRL receptors.

OBJECTIVE

To study PRL and insulin ultradian rhythm and subcutaneous adipose tissue LPL mRNA and protein expressions in severely obese women before and after malabsorptive bariatric surgery.

METHODS AND PROCEDURES

Seven severely obese, fertile women were studied twice, once before and the second time 1 year after bilio-pancreatic diversion (BPD), when the weight was stable for at least 3 months. Metabolizable energy intake and 24-h energy expenditure (EE) were measured. Fourier and PULSEFIT analyses were applied to 24-h hormonal time-series to study daily fluctuations and hormonal clearance. Insulin sensitivity was assessed by euglycemic-hyperinsulinemic clamp. Quantitative-competitive reverse transcriptase-PCR and western blot analysis were used to measure LPL gene expression.

RESULTS

Spontaneous 24-h PRL secretion was significantly reduced after BPD (mean-daily release, 128.4 +/- 28.1 microg/l vs. 67.2 +/- 9.2 microg/l distribution volume (Vd/l.24 h), P = 0.02); insulin secretion also was significantly reduced (499.9 +/- 204.0 microg/Vd/l.24 h vs. 85.6 +/- 21.0 microg/Vd/l.24 h, P = 0.0001). Metabolizable energy/kg(FFM) did not change significantly after BPD. Twenty-four-hour EE, but not 24-h EE/FFM, was significantly decreased after BPD (P < 0.05). Insulin sensitivity significantly (P < 0.0001) increased after BPD from 21.41 +/- 1.92 to 68.62 +/- 5.03 micromol/kg(FFM)/min. LPL mRNA concentration (from 42.63 +/- 4.21% to 19.00 +/- 2.74% of cyclophilin mRNA, P = 0.001) as well as LPL protein level (from 8.94 +/- 2.73 to 3.16 +/- 1.05 as ratios of protein of interest vs. housekeeping protein, P = 0.038) significantly decreased after BPD. The major determinant of PRL secretion was insulin secretion, whereas the best predictors of LPL expression were insulin and PRL secretion rates.

DISCUSSION

The restriction of lipid metabolizable energy rather than weight loss seems to be responsible for both reduction in PRL circulating levels and normalization of its secretion rhythm after bariatric surgery. Furthermore, the reduced adipose tissue LPL expression, being significantly correlated with the decrease in insulin and PRL, suggests a role of hyperinsulinemia and hyperprolactinemia in inducing and sustaining obesity.

Hyperprolactinaemia

Hyperprolactinaemia is a frequent cause of reproductive problems encountered in clinical practice. A variety of pathophysiological conditions can lead to hyperprolactinaemia; therefore, pregnancy, drug effects, hypothyroidism and polycystic ovary syndrome should be excluded before investigating for prolactin-secreting pituitary tumours. Prolactinomas are mainly diagnosed in women aged 20-40 years. They present with clinical features of hyperprolactinaemia (galactorrhoea, gonadal dysfunction), and more rarely with large tumours, headache and visual field loss due to optic chiasm compression. Medical therapy with dopamine agonists is the treatment of choice for both micro- and macroprolactinomas. Tumour shrinkage and restoration of gonadal function are achieved in the majority of cases with dopamine agonists. A trial of withdrawal of medical therapy may be considered in many patients with close follow-up. Pituitary surgery and radiotherapy currently have very limited indications. Pregnancies in patients with prolactinomas need careful planning and close monitoring.

What can we learn from rodents about prolactin in humans?

Prolactin (PRL) is a 23-kDa protein hormone that binds to a single-span membrane receptor, a member of the cytokine receptor superfamily, and exerts its action via several interacting signaling pathways. PRL is a multifunctional hormone that affects multiple reproductive and metabolic functions and is also involved in tumorigenicity. In addition to being a classical pituitary hormone, PRL in humans is produced by many tissues throughout the body where it acts as a cytokine. The objective of this review is to compare and contrast multiple aspects of PRL, from structure to regulation, and from physiology to pathology in rats, mice, and humans. At each juncture, questions are raised whether, or to what extent, data from rodents are relevant to PRL homeostasis in humans. Most current knowledge on PRL has been obtained from studies with rats and, more recently, from the use of transgenic mice. Although this information is indispensable for understanding PRL in human health and disease, there is sufficient disparity in the control of the production, distribution, and physiological functions of PRL among these species to warrant careful and judicial extrapolation to humans.

Body fat in nonobese women with prolactinoma treated with dopamine agonists

OBJECTIVES

To evaluate body fat in nonobese women with prolactinoma treated with dopamine agonists, using whole body dual energy X-ray absorptiometry (DXA) and to correlate DXA results with biochemical data and clinical aspects of the prolactinoma.

DESIGN, PATIENTS AND MEASUREMENTS

A cross-sectional study was performed in two University referral centres. Thirty-one nonobese premenopausal women with prolactinoma were subjected to DXA and blood analysis at clinical evaluation. They were compared with 21 control women of similar age and body mass index (BMI).

RESULTS

Women with prolactinoma treated with dopamine agonists and controls had similar body fat percentages in all sites evaluated with DXA (arms, legs, trunk, android, gynoid and total body). Patients with normal PRL levels at study entry had lower body fat percentages in all sites. In the patient group, arm, leg, truncal, android, gynoid and total body fat were positively associated with PRL levels.

CONCLUSION

Body fat percentage is similar in nonobese women with prolactinoma and in controls. The lower body fat content in patients with normal PRL levels is likely to be due to the metabolic effects of adequate dopamine receptor type 2 (DR2) activation as a result of regular dopamine agonist treatment. This finding reinforces the importance of the appropriate treatment with dopamine agonists in women with prolactinoma, which, besides normalizing PRL levels, reduces body fat content and the consequent risk of developing Metabolic Syndrome and its complications.

Adipocyte prolactin: regulation of release and putative functions

Pituitary-derived prolactin (PRL) is a well-known regulator of the lactating mammary gland. However, the recent discovery that human adipose tissue produces PRL as well as expresses the PRL receptor (PRLR) highlights a previously unappreciated action of PRL as a cytokine involved in adipose tissue function. Biologically active PRL is secreted by all adipose tissue depots examined: breast, visceral and subcutaneous. The expression of adipose PRL is regulated by a non-pituitary, alternative superdistal promoter. PRL expression and release increases during early pre-adipocyte differentiation and is stimulated by cyclic AMP activators, including beta adrenergic receptor agonists. PRL release from subcutaneous adipose explants is attenuated during obesity, suggesting that adipose PRL production is altered by the metabolic state. Several lines of evidence indicate that PRL suppresses lipid storage as well as the release of adipokines such as adiponectin, interleukin-6 and possibly leptin. PRL has also been implicated in the regulation of adipogenesis. A newly developed PRL-secreting human adipocyte cell line, LS14, should allow comprehensive examination of the regulation and function of adipocyte-derived PRL. Collectively, these studies raise the prospect that PRL affects energy homeostasis through its action as an adipokine and is involved in the manifestation of insulin resistance.

Hormonal induction of leptin resistance during pregnancy

Despite elevated plasma leptin, food intake is increased during pregnancy leading to fat deposition. We have demonstrated that intracerebroventricular (icv) leptin is unable to suppress food intake in pregnant rats, as it does in non-pregnant animals. Hence, central leptin resistance develops during pregnancy. These changes are physiologically appropriate, providing increased energy reserves to help meet the high metabolic demands of fetal development and lactation. To characterise this central leptin resistance, we have measured levels of leptin receptor (Ob-Rb) mRNA in the hypothalamus, and examined leptin-induced phosphorylation of STAT3 (pSTAT3) in specific regions of the hypothalamus. In addition, to investigate the mechanism underlying pregnancy-induced leptin resistance, we have investigated effects of hormone treatments on hypothalamic responses to leptin in a pseudopregnant rat model. We observed a significant reduction of Ob-Rb mRNA levels in the ventromedial hypothalamic nucleus (VMH) during pregnancy, with no changes detected in other hypothalamic nuclei. Levels of leptin-induced pSTAT3 were specifically suppressed in the VMH and arcuate nucleus of pregnant rats compared to non-pregnant rats. Pseudopregnant rats were hyperphagic but did not become leptin resistant, suggesting that fetal or placental factors are required for the induction of leptin resistance. These data implicate the VMH as a key hypothalamic site involved in hormone-induced leptin resistance during pregnancy, and suggest that placental hormone secretion may mediate the hormone-induced loss of response to leptin.

The prolactin-deficient mouse has an unaltered metabolic phenotype

Prolactin (PRL), best recognized for its lactogenic activity, is also involved in the regulation of metabolic homeostasis in both mammalian and nonmammalian species. Although several mouse models have been used to study the metabolic functions of PRL, a clear-cut consensus has not emerged given the limited and often conflicting data. To clarify the role of PRL in metabolic homeostasis in males and nonlactating females, we used the PRL-deficient mouse. Our objectives were to compare: 1) weight gain, 2) body composition, 3) serum lipid profile, 4) circulating leptin and adiponectin levels, and 5) glucose tolerance in PRL knockout, heterozygous, and wild-type mice maintained on standard chow, high-fat, or low-fat diets. In addition, we compared the lipolytic actions of PRL using adipose tissue explants from mice, rats, and humans. We are reporting that PRL deficiency does not affect the rate of weight gain, body composition, serum lipids, or adiponectin levels in either sex on any diet. Glucose tolerance was slightly impaired in very young PRL knockout male pups but not in adults or in females at any age. Leptin was elevated in male, but not female, PRL knockout mice maintained on a low-fat diet. PRL did not affect lipolysis in adipose tissue explants from mice but significantly inhibited glycerol release from both rat and human adipose explants in a dose-dependent manner. We conclude that PRL deficiency has negligible gross metabolic effects in mice.

Advances in the treatment of prolactinomas

Prolactinomas account for approximately 40% of all pituitary adenomas and are an important cause of hypogonadism and infertility. The ultimate goal of therapy for prolactinomas is restoration or achievement of eugonadism through the normalization of hyperprolactinemia and control of tumor mass. Medical therapy with dopamine agonists is highly effective in the majority of cases and represents the mainstay of therapy. Recent data indicating successful withdrawal of these agents in a subset of patients challenge the previously held concept that medical therapy is a lifelong requirement. Complicated situations, such as those encountered in resistance to dopamine agonists, pregnancy, and giant or malignant prolactinomas, may require multimodal therapy involving surgery, radiotherapy, or both. Progress in elucidating the mechanisms underlying the pathogenesis of prolactinomas may enable future development of novel molecular therapies for treatment-resistant cases. This review provides a critical analysis of the efficacy and safety of the various modes of therapy available for the treatment of patients with prolactinomas with an emphasis on challenging situations, a discussion of the data regarding withdrawal of medical therapy, and a foreshadowing of novel approaches to therapy that may become available in the future.

Melanin-concentrating hormone stimulates human growth hormone secretion: a novel effect of MCH on the hypothalamic-pituitary axis

Melanin-concentrating hormone (MCH), a 19-amino acid orexigenic (appetite-stimulating) hypothalamic peptide, is an important regulator of energy homeostasis. It is cleaved from its precursor prepro-MCH (ppMCH) along with several other neuropeptides whose roles are not fully defined. Because pituitary hormones such as growth hormone (GH), ACTH, and thyroid-stimulating hormone affect body weight and composition, appetite, insulin sensitivity, and lipoprotein metabolism, we investigated whether MCH exerts direct effects on the human pituitary to regulate energy balance using dispersed human fetal pituitaries (21-22 wk gestation) and cultured GH-secreting adenomas. We found that MCH receptor-1 (MCH-R1), but not MCH receptor-2, is expressed in both normal (fetal and adult) human pituitary tissues and in GH cell adenomas. MCH (10 nM) stimulated GH release from human fetal pituitary cultures by up to 62% during a 4-h incubation (P < 0.05). Interestingly, neuropeptide EI (10 nM), which is also cleaved from ppMCH, increased human GH secretion by up to 124% in fetal pituitaries. A milder, albeit significant, induction of GH secretion by MCH (20%) was seen in cultured GH-secreting pituitary adenomas. A comparable stimulation of GH secretion was seen when cultured mouse pituitary cells were treated with MCH. Treatment of cultured GH adenoma cells with MCH (100 nM) induced extracellular signal-regulated kinases 1 and 2 phosphorylation, suggesting activation of MCH-R1. In aggregate, these data suggest that MCH may regulate pituitary GH secretion and imply a potential cross-talk mechanism between appetite-regulating neuropeptides and pituitary hormones.

The influences of hyperprolactinemia and obesity on cardiovascular risk markers: effects of cabergoline therapy

OBJECTIVE

In view of the association of hyperprolactinaemia with insulin resistance, we hypothesized that patients with hyperprolactinaemia may present increased cardiovascular risk markers.

DESIGN

Descriptive clinical trial.

METHODS

Serum glucose, insulin, insulin resistance, lipids, high sensitivity C-reactive protein (hsCRP), interleukin (IL)-6, tumour necrosis factor (TNF)-alpha and soluble E-selectin (sELAM-1) serum levels were determined in 15 patients with hyperprolactinaemia at baseline (compared with 20 healthy subjects) and after 12 weeks of cabergoline therapy (0.5-1 mg twice per week). We also measured mononuclear cell NF-kappaB activation and TNF-alpha production in a subset of subjects.

RESULTS

Serum levels of prolactin (PRL), insulin, insulin resistance (HOMA-IR) index and hsCRP were significantly higher in patients than in control subjects. Markers of mononuclear cell activation did not differ between the groups. Hyperprolactinaemia, BMI and age were predictors of hsCRP. BMI was the only predictor of HOMA-IR. Cabergoline therapy significantly reduced serum PRL, insulin, hsCRP and sELAM-1 levels.

CONCLUSIONS

These data suggest that hyperprolactinaemia is associated with insulin resistance related to increased BMI and low-grade inflammation independently of BMI. Short-term cabergoline therapy can reduce the inflammatory markers.

Current treatment issues in female hyperprolactinaemia

High prolactin levels can occur as a physiological condition in females who are pregnant or lactating. As a pathological condition, hyperprolactinaemia is associated with gonadal dysfunction, infertility and an increased risk of long-term complications including osteoporosis. The most frequent cause of persistent hyperprolactinaemia is the presence of a micro- (<10mm diameter) or macroprolactinoma (>/=10mm). These pituitary tumours may produce an excessive amount of prolactin or disrupt the normal delivery of dopamine from the hypothalamus to the pituitary; prolactin secretion from the pituitary is inhibited by dopamine released from neurones in the hypothalamus. Medications including anti-psychotics can induce hyperprolactinaemia, while idiopathic hyperprolactinaemia accounts for 30-40% of cases. The prevalence of hyperprolactinaemia is difficult to establish as not all sufferers are symptomatic or concerned by their symptoms and may remain undiagnosed. Symptoms of hyperprolactinaemia include signs of hypogonadism, with oligomenorrhoea, amenorrhoea and galactorrhoea frequently observed. Pharmacological intervention should be considered the first line therapy and involves the use of dopamine agonists to reduce tumour size and prolactin levels. Bromocriptine has the longest history of use and is a well-established, inexpensive, safe and effective therapy option. However, bromocriptine requires multiple daily dosing and some patients are resistant or intolerant to this therapy. The two newer dopamine agonists, quinagolide and cabergoline, provide more effective and better tolerated treatments compared with bromocriptine and may offer effective therapies for bromocriptine-resistant or intolerant patients. Quinagolide can be used until pregnancy is confirmed and may result in improved compliance in females wishing to become pregnant. For patients with hyperprolactinaemia, pregnancy is safe and can frequently be beneficial, inducing a decrease in prolactin levels. There does not appear to be any increased risk of abortion, malformations or multiple births in pregnancies achieved with bromocriptine and this dopamine agonist can be used safely during pregnancy. Surgery should be considered only in certain circumstances, and for the majority of patients, dopamine agonists will be sufficient to alleviate symptoms and restore normal prolactin levels.

Focus on prolactin as a metabolic hormone

New information about the effects of prolactin (PRL) on metabolic processes warrants re-evaluation of the overall metabolic actions of PRL. PRL affects metabolic homeostasis by regulating key enzymes and transporters that are associated with glucose and lipid metabolism in several target organs. In the lactating mammary gland, PRL increases the production of milk proteins, lactose and lipids. In adipose tissue, PRL generally suppresses lipid storage and adipokine release. PRL supports the growth of pancreatic islets, stimulates insulin secretion and increases citrate production in the prostate. A specific case is made for PRL in the human breast and adipose tissue, where it acts as a circulating hormone and an autocrine or paracrine factor. Although the overall effects of PRL on body composition are modest and species specific, PRL might be involved in the manifestation of insulin resistance.

Endocrinological and auxological abnormalities in young children with optic nerve hypoplasia: a prospective study

OBJECTIVE

To determine the prevalence of endocrinopathies, neuroradiographical findings, and growth derangements in young children with optic nerve hypoplasia (ONH).

STUDY DESIGN

A prospective observational study examined the prevalence of endocrinopathies at study enrollment and growth patterns in children with ONH. Subjects (n = 47, mean +/- SD 15.2 +/- 10.6 months) were followed until 59.0 +/- 6.2 months of age.

RESULTS

The prevalence of endocrinopathies was 71.7%: 64.1% of subjects had growth hormone (GH) axis abnormalities, 48.5% hyperprolactinemia, 34.9% hypothyroidism, 17.1% adrenal insufficiency, and 4.3% diabetes insipidus (DI). Endocrinopathies were not associated with ONH laterality, absence of the septum pellucidum, or pituitary abnormalities on neuroimaging. End height standard deviation score (SDS) was similar to start length SDS independent of GH surrogate status. A significant increase in end weight SDS was found for the cohort (p < .001). A body mass index (BMI) >85th percentile was noted in 44.4% of the cohort and in 52.1% of subjects with GH axis abnormalities. Initial hyperprolactinemia was positively associated with increased end BMI SDS (p = .004).

CONCLUSIONS

These prospective findings confirm the high prevalence of pituitary endocrinopathies in children with ONH reported in previous retrospective studies. Our data reveal that some of these children maintain normal height velocity despite GH axis abnormalities, and, as a group, they are at high risk for increased BMI.

Reversible weight gain and prolactin levels--long-term follow-up in childhood

In adult patients weight gain is a frequent complaint of hyperprolactinaemia and it has been associated with a high prevalence of obesity. Normalization of prolactin (PRL) levels result in weight loss. The nature of this link is poorly defined. In this report we describe a 14 year-old female with primary amenorrhea and persistent progressive weight gain. The patient's height, weight and BMI were 152 cm, 70 kg, and 30.3 kg/m2, respectively. Basal hormonal investigation showed normal free thyroxin, TSH, IGF-I, cortisol and ACTH values. Serum PRL level was very high (16,278 mIU/l; normal range 63-426 mIU/l). Magnetic resonance imaging scan showed the presence of a pituitary microadenoma. Treatment with the non-selective dopamine agonist pergolide caused a significant reduction of serum PRL concentration with a remarkable decrease of body weight. During follow-up, repeat MRI scan revealed disappearance of the microadenoma. The reduction of the daily dose of pergolide was associated with an increase of serum PRL with significant weight gain. A further reduction of body weight was subsequently observed with an increase of pergolide dosage. Serum PRL measurement may be useful as part of the endocrine work-up of obese children with a history of unexplained recent weight gain, especially if associated with pituitary-gonadal axis dysfunction. The relationship between PRL secretion and weight change needs to be examined in prospective larger studies.

The regulation of fatty acid synthase by STAT5A

Growth hormone (GH) diminishes adipose tissue mass in vivo and decreases expression and activity of fatty acid synthase (FAS) in adipocytes. GH and prolactin (PRL) are potent activators of STAT5 and exert adipogenic and antiadipogenic effects in adipocytes. In this study, we demonstrate that GH and PRL decrease the mRNA and protein levels of FAS in 3T3-L1 adipocytes. We present evidence that indicates that FAS is repressed at the level of transcription. In addition, PRL responsiveness was shown to exist between -1,594 and -700 of the rat FAS promoter. Moreover, responsiveness to PRL was abolished with mutation of a site at position -908 to -893, which we have shown to bind STAT5A in a PRL-dependent manner. Taken together, these data strongly suggest that PRL directly represses expression of FAS in adipocytes through STAT5A binding to the -908 to -893 site. Furthermore, our results indicate that STAT5A has an antilipogenic function in adipocytes and may contribute to the regulation of energy balance.

Endocrine and neuroanatomic features associated with weight gain and obesity in adult patients with hypothalamic damage

PURPOSE

Obesity is a common consequence in patients with tumors of the hypothalamic region and of related treatment in children. Much less information is available on adult patients and long-term survivors. The aims of this study were to estimate the prevalence of obesity in adult patients with acquired structural hypothalamic damage and to define the characteristics of patients at greatest risk of obesity.

METHODS

A retrospective study was conducted of 52 patients (25 women; median age at diagnosis, 44 years; range, 17 to 78 years) with tumors involving the hypothalamic region. These included 22 craniopharyngiomas, 24 pituitary adenomas, and six other hypothalamic tumors. Changes in body mass index were determined, magnetic resonance imaging scans were scored by a radiologist for tumor size and the extent of involvement of the hypothalamus, and current hormone replacement therapy was recorded, to identify possible features associated with new or worsened obesity (defined as a body mass index > or =30 kg/m(2) at the latest follow-up, which had increased by at least 2 kg/m(2) since diagnosis of the tumor).

RESULTS

Serial body mass index data from diagnosis to the latest follow-up were available for 42 patients. After a median of 5 years (range, 1 to 19 years) of follow-up, most patients with hypothalamic damage were obese (52% [n = 22] vs. 24% [n = 10] at the time of diagnosis, P < 0.0001). In a multivariate model, use of desmopressin (odds ratio [OR] = 13; 95% confidence interval [CI]: 2.0 to 86; P = 0.007) and growth hormone replacement (OR = 7.6; 95% CI: 1.1 to 51; P = 0.04) were associated with new or worsened obesity during follow-up. No correlation was found between the initial size or location of the tumor and subsequent weight gain.

CONCLUSION

Obesity is highly prevalent in adult survivors of hypothalamic tumors. Use of desmopressin and growth hormone therapy, but not size or location of the tumor, were associated with weight gain and obesity following diagnosis. These findings may be helpful in identifying patients at increased risk of obesity, to whom earlier intervention could be offered.

Prolactin and reproductive medicine

PURPOSE OF REVIEW

This review aims to summarize current knowledge about prolactin, and outlines recent information that affects the management of patients with hyperprolactinaemia.

RECENT FINDINGS

The actions of prolactin have been clarified by studies of prolactin-receptor-deficient mice, which have a clear phenotype of reproductive failure at multiple sites. The treatment of patients with hyperprolactinaemia or prolactinoma is largely achieved using dopamine agonist drugs, which induce the shrinkage of pituitary prolactinomas as well as control of the endocrine syndrome. Recent findings indicate that successful cabergoline treatment may be able to induce long-term remission, allowing drug withdrawal in a substantial proportion of patients.

SUMMARY

At present, dopamine agonist drugs remain the best treatment for hyperprolactinaemic patients, and can help most affected women achieve pregnancy. Future work is likely to help understand the basis of long-term remission in patients with pituitary prolactinomas.

[Clinical and therapeutic aspects of prolactinoma in men]

Macroprolactinomas predominate in males in comparison to microprolactinomas, with greater trend to invasiveness than in females. The clinical treatment has been the first option to prolactinomas, in both macro and microadenomas, irrespective the sex. We compared clinical presentation, prolactin levels, neuroradiologic invasiveness and prolactinemia response of 23 men with prolactinomas subjected to clinical therapy (group 1) with 19 who went also through surgical and/or radiotherapeutic treatment (group 2). The statistical analysis was done by the tests of chi-square or exact of Fisher, in order to compare proportions, and by t of Student or Mann-Whitney, in order to compare means. The level of significance adopted was 5% (p<0.05). The two groups were similar regarding age (p=0.23), period between start of the first symptom and diagnosis (p=0.82), prolactin levels before treatment (p=0.41) and invasive macroadenomas proportion (p=0.096). There was significantly greater percentage of headache (p=0.009) and visual deficit (p=0.025) in group 2, as well as the drug usage (p=0.007) and observation (p=0.0005) periods were superior in this group. The variations of prolactin levels before and after therapy (p=0.49) as well as the percentage of prolactin normalization (p=0.20) did not show any significant difference when comparing the two groups. We conclude, emphasizing the relevance of precocious prolactinoma diagnostic in men, because of the demonstrated morbidity. We strengthen the use of dopamine agonist as the first therapeutic option irrespective the adenoma size.

Prevalence and correlates of obesity in a community sample of individuals with severe and persistent mental illness

Individuals with severe and persistent mental illness (SPMI) have a preponderance of weight problems, possibly even greater than the obesity epidemic in the general population. Although atypical antipsychotics cause weight gain, their contribution to obesity has not been characterized in a community setting where individuals may take multiple psychotropics associated with weight gain. Using survey information including measured height and weight from a random sample of Maryland Medicaid recipients with SPMI, we compared obesity prevalence to the National Health and Nutrition Examination Survey (NHANES III) sample and a Maryland sample (Behavioral Risk Factor Surveillance System) of the general population adjusted to SPMI demographic characteristics. We investigated correlates of obesity in the SPMI sample. The results indicate that both men and especially women with SPMI had a higher prevalence of obesity than the general population; this portends substantial health implications. A fourfold association between atypical antipsychotics and prevalent obesity was found in men but not in women; further work should clarify mechanisms of obesity in the SPMI.

Hyperprolactinemia: pathophysiology and management

Hyperprolactinemia is commonly found in both female and male patients with abnormal sexual and/or reproductive function or with galactorrhea. If serum prolactin levels are above 200 microg/L, a prolactin-secreting pituitary adenoma (prolactinoma) is the underlying cause, but if levels are lower, differential diagnoses include the intake of various drugs, compression of the pituitary stalk by other pathology, hypothyroidism, renal failure, cirrhosis, chest wall lesions, or idiopathic hyperprolactinemia. When a pituitary tumor is present, patients often have pressure symptoms in addition to endocrine dysfunction, such as headaches, visual field defects, or cranial nerve deficits. The large majority of patients with prolactinomas, both micro- and macroprolactinomas, can be successfully treated with dopaminergic drugs as first-line treatment, with normalization of prolactin secretion and gonadal function, and with significant tumor shrinkage in a high percentage of cases. Surgical resection of the prolactinoma is the option for patients who may refuse or do not respond to long-term pharmacological therapy. Radiotherapy and/or estrogens are also reasonable choices if surgery fails. In patients with asymptomatic microprolactinoma no treatment needs to be given and a regular follow-up with serial prolactin measurements and pituitary imaging should be organized. Currently, the most commonly used dopamine agonists are bromocriptine, pergolide, quinagolide and cabergoline. When comparing the plasma half-life, efficacy and tolerability of these drugs, cabergoline seems to have the most favorable profile, followed by quinagolide. Ifprolactin levels are well controlled with dopamine agonist therapy, gradual tapering of the dose to the lowest effective amount is recommended, and in a number of cases medication can be stopped after several years. Evidence to date suggests that cabergoline and quinagolide appear to have a good safety profile for women who wish to conceive, but hard evidence proving that dopamine agonists do not provoke congenital malformations when taken during early pregnancy is currently only available for bromocriptine. Once pregnant, dopamine agonist therapy should be immediately stopped, unless growth of a macroprolactinoma is likely or pressure symptoms occur. At our institution patients with symptomatic prolactinomas, both micro- and macroadenomas, are treated with cabergoline as the first-line aproach. In the small group of patients who do not respond to this treatment, or who refuse long-term therapy, surgery is offered. Radiotherapy is given if both pharmacologic therapy and surgery fail.

Pituitary tumor endocrinopathies and their endocrine evaluation

Pituitary tumors, depending on their respective cell type, manifest various endocrinopathies. Prolactinomas may present as hypogonadism and galactorrhea and can be diagnosed by measuring morning prolactin levels. Gonadotropinomas rarely cause gonadal hyperstimulation, and dynamic thyrotropin-releasing hormone stimulation testing is often required to elicit a diagnostic gonadotropin and/or subunit secretory response. Acromegaly is a multisystemic debilitating disease for which early diagnosis and treatment are crucial. Diagnostic criteria include a lack of plasma growth hormone suppression during the oral glucose tolerance test and elevation of age- and sex-matched insulin growth factor-1 levels. Patients harboring corticotropin-secreting adenomas characheristically present with signs and symptoms of hypercortisolism. Inferior petrosal sinus sampling for corticotropin may be required for microadenoma localization. Thyrotropinomas produce inappropriate thyrotropin (TSH) secretion and hyperthyroidism. The new third-generation TSH assay has improved the rate of detection of these lesions at an earlier stage.

The antipsychotic drug sulpiride does not affect bodyweight in male rats. Is insulin resistance involved?

Previous studies have shown that prolonged administration of antipsychotic drugs induces obesity in female but not in male rats. To explore the mechanisms involved in this sex-dependent effect, we administered the dopamine antagonist sulpiride (20 mg/kg i.p.) or vehicle (0.1 N HCl) to adult male rats during 21 days and daily assessed bodyweight and food intake. Then, we evaluated the glucose tolerance and the serum levels of insulin, leptin, total testosterone, dehydroepiandrosterone-sulfate (DHEA-S), thyroid hormones and blood lipids. In another experiment, food intake and water intake were assessed after acute injections of sulpiride or vehicle into the perifornical lateral hypothalamus. Lastly, the dopamine metabolites dihydroxyphenylacetic acid (DOPAC) and homovanilic acid (HVA) in the lateral hypothalamus were assessed by in vivo microdialysis after acute systemic injections of sulpiride and vehicle. Chronic sulpiride administration did not affect bodyweight gain and food intake. However, prolactin levels and the area under the glucose and insulin curves were significantly elevated. Acute sulpiride significantly increased food intake, water intake, DOPAC and HVA levels. The acute effects of sulpiride show that this drug is active at the perifornical lateral hypothalamus, which is a brain area where blockade of dopamine receptors stimulates feeding. However, after prolonged administration, sulpiride did not affect body weight. This lack of effect may be related to the impairment of insulin sensitivity, which may prevent body weight gain, and counteract other effects of sulpiride that promote adiposity such as hyperprolactinemia. These findings noticeably contrast with those observed in sulpiride-treated female rats that appear to display enhanced insulin sensitivity. The changes in insulin sensitivity do not appear related to a decrease in androgenic activity, because testosterone and DHEA-S levels were not affected by sulpiride. However, these results should be considered as preliminary because other relevant endocrine variables such as free testosterone, steroid binding globulin and pituitary gonadotrophin levels were not evaluated. Since the same sex-dependent effect on body weight and food intake in rats has been observed during administration of risperidone, which has a different pharmacological profile than sulpiride, future studies must evaluate other neurotransmitters involved in food intake regulation such as serotonin, noradrenaline and histamine.

Antipsychotic drugs and obesity: is prolactin involved?

OBJECTIVES

To correlate the anthropometric indexes (Body Mass Index [BMI] and Waist-Hip ratio [WHR]) with the serum prolactin levels in a heterogeneous population of patients treated with typical antipsychotic (AP) drugs.

METHODS

We evaluated BMI, WHR, and fasting serum prolactin of inpatients (n = 105) and outpatients (n = 122) treated with APs, in outpatients receiving other psychotropic drugs (OPDs) (n = 77), and in drug-free subjects (n = 33). Outpatients had free access to food, whereas the inpatient sample comprised people with a monotonous diet of approximately 2000 Kcal daily.

RESULTS

Prolactin correlated positively with the BMI in the whole group of AP-treated outpatient men (P = 0.03) and with the WHR in AP-treated inpatient men (P = 0.053). Regarding treatment duration, prolactin and BMI correlated positively in men consecutively treated for more than 1 year (P = 0.023). By contrast, a trend toward a negative correlation between prolactin and BMI was observed in AP-treated outpatient women (P = 0.08). No significant correlation, or even a trend, was observed in the other groups.

CONCLUSIONS

Prolactin may be involved in AP-induced weight gain, particularly in men. Future studies should characterize the period of maximal prolactin impact on body weight during AP treatment. Specific populations particularly sensitive to hyperprolactinemia might be identified as well. The negative correlation between prolactin and BMI detected in AP-treated women resembles the dampened prolactin response observed in severe primary obesity.

Body weight and fat deposition in prolactin receptor-deficient mice

To explore the roles of the lactogens in adipose tissue development and function, we measured body weight, abdominal fat content, and plasma leptin concentrations in a unique model of lactogen resistance: the PRL receptor (PRLR)-deficient mouse. The absence of PRLRs in knockout mice was accompanied by a small (5-12%), but progressive, reduction in body weight after 16 weeks of age. Females were affected to a greater degree than males. The reduction in weight in female PRLR-deficient mice (age 8-9 months) was associated with a 49% reduction in total abdominal fat mass and a 29% reduction in fat mass expressed as a percentage of body weight. Lesser reductions were noted in male mice. Plasma leptin concentrations were reduced in females but not in males. That the reductions in abdominal fat may reflect in part the absence of lactogen action in the adipocyte is suggested by the demonstration of PRLR messenger RNA in normal mouse white adipose tissue. Nevertheless, steady state levels of PRLR messenger RNA in mature adipocytes are very low, suggesting that the effects of lactogens might be mediated by other hormones or cellular growth factors. Our observations suggest roles for the lactogens in adipose tissue growth and metabolism in pregnancy and postnatal life.

Leptin and leptin receptor in anterior pituitary function

Leptin is a 16 kDa protein that exerts important effects on the regulation of food intake and energy expenditure by interacting with the leptin receptor in the brain and in many other tissues. Although leptin is produced mainly by white adipose tissue, several laboratories have shown low levels of leptin production by a growing number of tissues including the anterior pituitary gland. Many studies have implicated leptin in anterior pituitary function including the observation that homozygous mutations of the leptin receptor gene led to morbid obesity, lack of pubertal development and decreased GH and TSH secretion. In addition, leptin functions as a neuroendocrine hormone and regulates many metabolic activities. Leptin also interacts with and regulates the hypothalamic-pituitary-adrenal, the hypothalamic-pituitary-thyroid and the hypothalamic-pituitary-gonadal axes. All of the anterior pituitary cell types express the leptin receptor. However, leptin has been localized in specific subtypes of anterior pituitary cells indicating cell type-specific production of leptin in the anterior pituitary. Subcellular localization of leptin indicates co-storage with secretory granules and implicates hypothalamic releasing hormones in leptin secretion from anterior pituitary hormone cells. Leptin signal transduction in the anterior pituitary has been shown to involve the janus protein-tyrosine kinase (JAK)/signal transducer and activation of transcription (STAT) as well as suppressor of cytokine signalling (SOCS). These proteins are activated by tyrosine-phosphorylation in anterior pituitary cells. The various steps in pituitary leptin signal transduction remain to be elucidated.

Naltrexone does not prevent the weight gain and hyperphagia induced by the antipsychotic drug sulpiride in rats

Few pharmacological tools are currently available to counteract the excessive body weight gain often observed during prolonged administration of antipsychotic drugs. Most antipsychotic drugs block dopamine receptors, and both the brain dopaminergic and opioid systems appear to be involved in initiation and maintenance of feeding behavior, respectively. We evaluated whether the opioid antagonist naltrexone (NAL, 0.5-16 mg/kg/ip for 21 days) (a) affects body weight and food intake in gonadally-intact and drug-free female rats, (b) prevents obesity, hyperphagia, hyperprolactinemia and vaginal cycle disruption induced by long-term administration of the antipsychotic drug sulpiride (SUL, 20 mg/kg/ip for 21 days), or (c) reverses the acute hyperphagia induced by SUL (15 microg bilaterally), when directly applied in the perifornical lateral hypothalamus (PFLH). In drug-free rats, only NAL doses above 4 mg/kg, significantly decreased weight gain and food intake. Even though NAL (1 and 8 mg/kg) significantly attenuated SUL-induced hyperphagia and hyperprolactinemia, it did not reverse at any dose the weight gain and permanent diestrous induced by SUL. In addition, local NAL did not prevent the hyperphagia and polidypsia observed after acute intrahypothalamic SUL. Unexpectedly, the cumulative and 24 h food intake in SUL-treated rats was significantly increased by NAL. Collectively, these results do not support a role for endogenous opiates in the neural and endocrine mechanisms involved in weight gain during prolonged antipsychotic drug administration in rats.

Prolactin stimulates leptin secretion by rat white adipose tissue

Leptin, the obese (Ob) gene product, is an adipocyte-derived satiety factor that is involved in the regulation of food intake and body weight. Leptin signals nutritional status to several other physiological systems and modulates their function. As PRL is involved in energy and lipid metabolism, this study was undertaken to investigate the role of PRL on in vivo regulation of leptin serum concentration and Ob messenger RNA expression in white adipose tissue in rats. It was found that increased serum PRL levels, obtained by pituitary graft or exogenous injected ovine PRL (oPRL, 5 mg/kg), significantly stimulate serum leptin concentration. A significant increase (P < 0.01) in serum leptin concentration was present in hyperprolactinemic animals (4.7+/-0.4 microg/liter) in comparison to controls (1.2+/-0.1 microg/liter and 1.09+/-0.09 microg/liter of intact sham operated and ovariectomized rats, respectively). Similar results were obtained in oPRL-treated animals where leptin levels were 5.4+/-0.1 microg/liter vs. 1.1+/-0.1 microg/liter and 0.8+/-0.08 microg/liter of intact sham operated rats and ovariectomized, respectively (P < 0.001). This stimulatory effect of PRL on serum leptin levels was significantly reduced by food deprivation (P < 0.01) where serum leptin levels were 12.5+/-0.65 microg/liter in grafted animals vs. 3.2+/-0.36 microg/liter of grafted animals subjected to 48 h of food deprivation. Moreover, in vivo, PRL was able to induce leptin messenger RNA levels in several areas of rat white adipose tissue. The data demonstrate that PRL acts on the adipose tissue increasing leptin synthesis and secretion, suggesting a new role for this lactogenic hormone in the regulation of food intake.

Clinical management of prolactinomas

Prolactinomas are benign, sporadic pituitary tumours that typically present with amenorrhoea and galactorrhoea in women, and hypogonadism and space-occupying effects in men. Hyperprolactinaemic hypogonadism in either sex is associated with reduced bone mineral density, which may be progressive and only partially reversible. For most microprolactinomas, dopamine agonists are the treatment of choice, achieving normoprolactinaemia and restoring gonadal function in 80-90% of cases. Trans-sphenoidal surgery is curative in 60%, but may be complicated by hypopituitarism and is usually reserved for patients with dopamine agonist intolerance or resistance. A subgroup of patients with small tumours, mild symptoms and normal gonadal function may be monitored without specific treatment--the risk of tumour expansion is small. Macroprolactinomas should be treated medically, dopamine agonists controlling prolactin secretion and achieving significant tumour shrinkage in 80% of cases, whereas surgery is curative in only a quarter. Cabergoline is the dopamine agonist of choice in most situations, being better tolerated and more effective than bromocriptine. Quinagolide is an effective alternative. Dopamine agonist withdrawal or dose reduction should be considered after 2-5 years therapy. Oestrogens may be used with caution in women with prolactinomas.

Neuroendocrine regulation and actions of leptin

The discovery of the adipocyte-produced hormone leptin has greatly changed the field of obesity research and our understanding of energy homeostasis. It is now accepted that leptin is the afferent loop informing the hypothalamus about the state of fat stores, with hypothalamic efferents regulating appetite and energy expenditure. In addition, leptin has a role as a metabolic adaptator in overweight and fasting states. New and previously unsuspected neuroendocrine roles have emerged for leptin. In reproduction, leptin is implicated in fertility regulation, and it is a permissive factor for puberty. Relevant gender-based differences in leptin levels exist, with higher levels in women at birth, which persist throughout life. In adult life, there is experimental evidence that leptin is a permissive factor for the ovarian cycle, with a regulatory role exerted at the hypothalamic, pituitary, and gonadal levels, and with unexplained changes in pregnancy and postpartum. Leptin is present in human milk and may play a role in the adaptive responses of the newborn. Leptin plays a role in the neuroendocrine control of GH secretion, through a complex interaction at hypothalamic levels with GHRH and somatostatin. Leptin participates in the expression of CRH in the hypothalamus, interacts at the adrenal level with ACTH, and is regulated by glucocorticoids. Since leptin and cortisol show an inverse circadian rhythm, it has been suggested that a regulatory feedback is present. Finally, regulatory actions on TRH-TSH and PRL secretion have been found. Thus leptin reports the state of fat stores to the hypothalamus and other neuroendocrine areas, and the neuroendocrine systems adapt their function to the current status of energy homeostasis and fat stores.