Low prolactin levels are associated with visceral adipocyte hypertrophy and insulin resistance in humans

Abnormally Increased Prolactin Levels in Women with Polycystic Ovarian Syndrome Are Associated with Risk of Obesity, Insulin Resistance and Prediabetes

Polycystic ovarian syndrome (PCOS) is a prevalent endocrine condition in women of reproductive age, characterized also by insulin resistance, affecting both obese and non-obese individuals. Hyperprolactinemia in patients with PCOS may additionally aggravate the decline in insulin sensitivity, attributable to prolactin lipogenic effects and influence on metabolic profile. Therefore, this study aimed to investigate the serum levels of prolactin in women with PCOS and their associations with obesity, insulin resistance and prediabetes. A retrospective monocentric study was performed using the electronic database of 157 women diagnosed with PCOS. Serum prolactin, BMI, complete glucose-insulin profile and insulin resistance indices following OGTT were determined. The women with hyperprolactinemia (40.8%) had significantly higher BMI (p = 0.007), fasting glucose (p = 0.003), insulin levels (p < 0.001) and HOMA-IR (p < 0.001). The women with PCOS categorized as overweight/obese (47.1%), insulin resistant (68.8%), having impaired fasting glycaemia (28.7%) and prediabetes (36.3%) showed significantly higher levels of prolactin compared to the respective counterparts. Consequently, higher prolactin levels were significantly associated with an elevated risk of development of overweight/obesity (OR 2.59; 95% CI: 1.34-4.97, p = 0.004), insulin resistance (OR 3.33; 95% CI: 1.54-7.19, p = 0.002) and prediabetes (OR 1.98; 95% CI: 1.02-3.85, p = 0.043) in women with PCOS. Our results suggest that hyperprolactinemia might be a pathophysiological link between obesity, insulin resistance, and carbohydrate metabolism impairments in patients with PCOS. Increased prolactin levels may serve as an additional indicator of insulin resistance and even further exacerbate it in women with PCOS.

Scientific Progress in Polycystic Ovary Syndrome: Little by Little

New international recommendations on the diagnosis and treatment of polycystic ovary syndrome (PCOS) were published in autumn 2023 [...].

A Retrospective Study in Trans Individuals Undergoing Gender Affirming Testosterone Treatment: Can Changes in Prolactin Counteract the Negative Effects on the Lipid Profile?

Background/Objectives: Gender-affirming hormone therapy (GAHT) is known to influence the lipid profiles of trans men and transmasculine individuals. Recent data show that moderate prolactin (PRL) elevations might exert beneficial metabolic effects ("HomeoFIT-PRL model"). The aim of this study is to investigate changes in PRL levels and possible associations between PRL and lipid profiles in this population after a year of GAHT. Methods: In a retrospective cohort study, 97 participants, who received GAHT with testosterone, were included. Blood lipids, PRL, and sex steroid hormone levels were evaluated prior to and at 10-14 months after treatment started. Results: The difference in PRL levels between baseline and follow-up was significant (p = 0.007) with a median difference of +2.3 ng/mL. Concerning blood lipids, the decline in high-density lipoprotein cholesterol (HDL-C) reached statistical significance (median 56 mg/dL versus 50 mg/dL; p < 0.001), and low-density lipoprotein cholesterol (LDL-C) and triglyceride levels increased (p = 0.023 and p = 0.045, respectively). Individuals with a PRL > 25 ng/mL at follow-up (n = 20, 20.6%) revealed increases in total cholesterol and LDL-C significantly less often. Overall, participants frequently displayed unfavorable changes in their lipid profile after 10-14 months of GAHT, as well as a slight but significant increase in PRL. About 20% of patients showed mild-to-moderate hyperprolactinemia (PRL > 25 ng/mL). However, such changes were associated with potentially beneficial dynamics in the lipid profile, at least for triglycerides. Conclusions: These findings seem in line with the HomeoFIT-PRL model suggesting that moderate elevations in PRL levels might exert beneficial metabolic effects. Increases in PRL after testosterone were common.

Changes in Prolactin and Insulin Resistance in PCOS Patients Undergoing Metformin Treatment: A Retrospective Study

Background: Prolactin levels have been shown to influence metabolic outcomes, including insulin resistance. Metformin is known to be beneficial in polycystic ovary syndrome (PCOS) patients. PCOS women might react differently to metformin treatment depending on their baseline prolactin levels. Methods: In this retrospective study, the homeostasis model assessment for insulin resistance (HOMA-IR), prolactin, luteinizing hormone (LH), follicle-stimulating hormone (FSH), the LH:FSH ratio, and total testosterone and sex hormone-binding globulin (SHBG) were measured in 75 obese/overweight women with PCOS and insulin resistance before initiation of metformin treatment and after 6-8 months. Results: At baseline, HOMA-IR was inversely correlated to SHBG (r = -0.408; p < 0.001) and prolactin (r = -0.402; p < 0.001). After 6-8 months of metformin treatment, the LH:FSH ratio and the HOMA-IR declined significantly (p < 0.05). A significant positive correlation could be shown between basal prolactin and the difference in the HOMA-IR (r = 0.233; p = 0.044). Women with lower baseline prolactin (≤14.9 ng/mL) revealed a sharper decline in HOMA-IR (-0.8, IQR -1.0; -0.5 vs. -0.6, IQR -0.8; -0.3; p = 0.049) as well as an increase in prolactin at follow-up (1.6 ng/mL, IQR -0.2;3.8 vs. -1.3, IQR -4.6;3.2; p = 0.003) compared to patients with a baseline prolactin > 14.9 ng/mL. Conclusions: In overweight/obese, insulin-resistant PCOS women, lower baseline prolactin levels are associated with higher baseline HOMA-IR levels as well as with a better response to metformin treatment. More data are necessary to prove these observations in larger populations.

What do we know about abnormally low prolactin levels in polycystic ovary syndrome? A narrative review

Hyper and hypoprolactinemia seem to be related to the occurrence of metabolic alterations in PCOS patients. In contrast, between significantly elevated and significantly low, prolactin levels seem to be protective against metabolic consequences. In the present review, we found 4 studies investigating hypoprolactinemia in patients with PCOS. We also identified 6 additional studies that reported low levels of PRL in PCOS patients. Although its prevalence is not considered high (13.2-13.9%), its contribution is certainly significant to the metabolic alterations observed in PCOS (insulin resistance, obesity, diabetes mellitus, and fatty liver disease). Dopamine inhibits the secretion of prolactin and GnRH. If dopamine levels are low or the dopamine receptor is less expressed or mutated, the levels of prolactin and GnRH increase, and consequently, LH also increases. On the other hand, hyperprolactinemia, in prolactinomas-typical levels, acting through kisspeptin inhibition causes GnRH suppression and hypogonadotropic hypogonadism. In situations of hypoprolactinemia due to excessive dopamine agonist treatment, dosage reduction is important to minimize the decrease in prolactin levels. Nevertheless, there is a lack of prospective studies confirming these hypotheses, as well as randomized clinical trials with appropriate drugs targeting both hyperprolactin and hypoprolactin in patients with PCOS.

The relationship between low prolactin and type 2 diabetes

Prolactin (PRL) is secreted throughout life in men and women. At elevated levels, its physiological role in pregnancy and lactation, and pathological effects, are well known. However clinical implications of low circulating PRL are not well established. We conducted a meta-analysis to examine the relationship between low PRL levels and type 2 diabetes. Five papers included cross-sectional studies comprising 8,720 men (mean age range 51.4-60 years) and 3,429 women (49.5-61.6 years), and four papers included cohort studies comprising 2,948 men (52.1-60.0 years) and 3,203 women (49.2-60.1 years). Individuals with pregnancy, lactation and hyperprolactinemia, drugs known to alter circulating PRL levels, or pituitary diseases had been excluded. Although most studies used quartiles to categorize PRL groups for analysis, PRL cut-off values (all measured by chemiluminescence immunoassay) were variably defined between studies: the lowest PRL quartiles ranged from 3.6 ng/ml to 7.2 ng/ml in men and between 4.5 ng/ml to 8 ng/ml in women; and the highest PRL quartiles ranged from 6.9 ng/ml to 13 ng/ml in men and 9.6 ng/ml to 15.8 ng/ml in women. Type 2 diabetes was defined variably using self-reported physician's diagnosis, fasting blood glucose, oral glucose tolerance test or glycated hemoglobin (HbA1C). In cross-sectional studies, compared to individuals in the highest PRL groups (reference), those in the lowest PRL groups had greater risk of type 2 diabetes both in men: odds ratio (OR) and 95% confidence interval = 1.86 (1.56-2.22) and in women: OR = 2.15 (1.63-2.85). In cohort studies, women showed a significant association between low PRL and type 2 diabetes: OR = 1.52 (1.02-2.28) but not men: OR = 1.44 (0.46-4.57). Relatively low heterogeneity was observed (I2 = 25-38.4%) for cross-sectional studies, but higher for cohort studies (I2 = 52.8-79.7%). In conclusion, low PRL is associated with type 2 diabetes, but discrepancy between men and women in the relationship within cohort studies requires further research.

The homeo-FIT-prolactin hypothesis: the role of prolactin in metabolic homeostasis - association or causality?

The homeo-fit-prolactin hypothesis proposes a causal metabolic role for prolactin with hypoprolactinemia and hyperprolactinemia leading to adverse metabolic alterations. However, prolactin within the normal range and up to four times the upper reference limit may be a consequence of metabolic adaption and have a positive metabolic role similar to increased insulin in pre-diabetes. As a consequence, drugs that would increase prolactin levels within this threshold may hold promising effects, particularly for patients with type 2 diabetes. A documented positive metabolic effect of prolactin just above the normal threshold would not just be of benefit to patients with diabetes but assist in the decision to treat mild hyperprolactinemia in other patient groups as well, e.g. drug-induced hyperprolactinemia or idiopathic hyperprolactinemia. Prolactin receptors are present in the pancreas, liver, and adipose tissue, and pre-clinical studies suggest a positive and causal effect of prolactin on the gluco-insulinemic profile and lipid metabolism. This narrative review examines the evidence for the homeo-fit-prolactin hypothesis with a particular focus on results from human studies.

The molecular basis of hypoprolactinaemia

Hypoprolactinaemia is an endocrinopathy which is typically encountered as part of a combined pituitary hormone deficiency picture. The vast majority of genetic causes identified to date have been in the context of congenital hypopituitarism with multiple co-existent endocrinopathies. This is primarily with its closest hormonal relation, namely growth hormone. Acquired hypoprolactinaemia is generally rare in paediatric patients, and usually occurs together with other hormonal deficiencies. Congenital hypopituitarism occurs with an incidence of 1:4,000-10,000 cases and mutations in the following transcription factors account for the majority of documented genetic causes: PROP-1, POU1F1, LHX3/4 as well as documented case reports for a smaller subset of transcription factors and other molecules implicated in lactotroph development and prolactin secretion. Isolated prolactin deficiency has been described in a number of sporadic case reports in the literature, but no cases of mutations in the gene have been described to date. A range of genetic polymorphisms affecting multiple components of the prolactin signalling pathway have been identified in the literature, ranging from RNA spliceosome mutations (RNPC3) to loss of function mutations in IGSF-1. As paediatricians gain a greater understanding of the long-term ramifications of hypoprolactinaemia in terms of metabolic syndrome, type 2 diabetes mellitus and impaired fertility, the expectation is that clinicians will measure prolactin more frequently over time. Ultimately, we will encounter further reports of hypoprolactinaemia-related clinical presentations with further genetic mutations, in turn leading to a greater insight into the molecular basis of hypoprolactinaemia in terms of signalling pathways and downstream mediators. In the interim, the greatest untapped reserve of genetic causes remains within the phenotypic spectrum of congenital hypopituitarism.

Cardiometabolic effects of hypoprolactinemia

The fall of PRL levels below the lower limit of the normal range configures the condition of hypoprolactinemia. Unlike PRL excess, whose clinical features and treatments are well established, hypoprolactinemia has been only recently described as a morbid entity requiring prompt identification and proper therapeutic approach. Particularly, hypoprolactinemia has been reported to be associated with the development of metabolic syndrome and impaired cardiometabolic health, as visceral obesity, insulin-resistance, diabetes mellitus, dyslipidaemia, chronic inflammation, and sexual dysfunction have been found more prevalent in patients with hypoprolactinemia as compared to those with normoprolactinemia. This evidence has been collected mainly in patients on chronic treatment with dopamine agonists for PRL excess due to a PRL-secreting pituitary tumour, and less frequently in those receiving the atypical antipsychotic aripiprazole. Nowadays, hypoprolactinemia appears to represent a novel and unexpected risk factor for cardiovascular diseases, as is the case for hyperprolactinemia. Nevertheless, current knowledge still lacks an accurate biochemical definition of hypoprolactinemia, since no clear PRL threshold has been established to rule in the diagnosis of PRL deficiency enabling early identification of those individual subjects with increased cardiovascular risk directly ascribable to the hormonal imbalance. The current review article focuses on the effects of hypoprolactinemia on the modulation of body weight, gluco-insulinemic and lipid profile, and provides latest knowledge about potential cardiovascular outcomes of hypoprolactinemia.

The beneficial and detrimental effects of prolactin hormone on metabolic syndrome: A double-edge sword

The metabolic syndrome (MetS) is a clustering of abdominal obesity, hypertension, hyperglycaemia, hypertriglyceridemia and low high-density lipoprotein (HDL) level. MetS development is affected by endocrine hormones such as prolactin (PRL) hormone which induce insulin resistance and central obesity because PRL is implicated in the pathogenesis of MetS. Pituitary PRL controls mammary gland, however extra-pituitary PRL is highly intricate in the regulation of adipose tissue function. In addition, cAMP activators enhance expression and release of PRL which involved in the control of lipogenesis and energy homeostasis. Consequently, hyperprolactinaemia may be associated with the development of MetS. However, normal physiological level of PRL is essential for insulin sensitivity and regulation of adipose tissue function and energy metabolism. Therefore, PRL has dual effects on the components of MetS. Hence, the present review aims to discuss the modulatory mechanistic role of PRL on MetS regarding its beneficial and detrimental effects.

Increased Cardiometabolic Risk in Men with Hypoprolactinemia: A Pilot Study

Low prolactin levels in men predispose them to mood disturbances, sexual dysfunction, and diabetes. The purpose of the current study was to assess cardiometabolic risk in males with hypoprolactinemia. This prospective study included three age-matched groups of young and middle-aged men: individuals with cabergoline-induced hypoprolactinemia (n = 15), cabergoline-treated subjects with prolactin levels within the reference range (n = 20), and untreated men with normal prolactin levels (n = 31). In men with hypoprolactinemia, the cabergoline dose was reduced in order to normalize prolactin concentration. Anthropometric parameters, blood pressure, QRISK3 score; plasma concentrations of prolactin, glucose, insulin, lipids, uric acid, high-sensitivity C-reactive protein (hsCRP), fibrinogen, homocysteine, and testosterone; whole-blood levels of glycated hemoglobin (HbA1C); urinary albumin-to-creatinine ratio (UACR); and carotid intima-media thickness were assessed at baseline and six months later. Men with hypoprolactinemia were characterized by higher body mass index, fat content, waist circumference, systolic blood pressure, fasting and 2 h post-load glucose, HbA1C, HOMA1-IR, uric acid, hsCRP, fibrinogen, homocysteine, and UACR; by lower HDL cholesterol and testosterone; by greater intima-media thickness; and by a higher QRISK3 score than their peers with normal prolactin levels. There were no statistically significant differences in the measured parameters between both groups of men with normal prolactin levels. Normalization of prolactin concentration was accompanied by normalization of biochemical variables, systolic blood pressure, and QRISK3 score. Although cabergoline dose reduction did not cause statistically significant changes in the remaining anthropometric parameters and intima-media thickness, six months later, they did not differ from those observed in the remaining study groups. Our findings suggest that iatrogenic hypoprolactinemia is associated with increased cardiometabolic risk, which is reversible and resolves after the normalization of prolactin levels.

Metabolic Syndrome in Reproductive Age Women of Various Ethnic Groups. Neuroendocrine Status and Lipid Peroxidation System

We analyzed the state of neuroendocrine regulation and LPO-antioxidant defense systems in reproductive age women with metabolic syndrome (MetS), representatives of the Russian and Buryat ethnic groups. Compared to the corresponding control groups, women from the Russian ethnic group with MetS had elevated levels of thyroid-stimulating hormone and free androgen index (FAI) and reduced levels of sex hormone-binding globulin, while women from the Buryat ethnic group had increased levels of prolactin and FAI. Changes in the LPO system in women of the Russian ethnic group with MetS consisted in an increase in the levels of substrates with double bonds, TBA-reactive substances, and fat-soluble vitamins. Buryat women with MetS had a higher content of primary oxidation products and reduced levels of glutathione. The results of the study indicate a hyperandrogenic shift in the neuroendocrine regulation system, as well as compensatory influences from different parts of the antioxidant defense system in women of reproductive age with MetS, depending on their ethnicity. These findings indicate the need for assessing and monitoring the levels of these metabolites in women with MetS, considering their ethnicity.

Comprehensive analysis of systemic, metabolic, and molecular changes following prospective change to low-carbohydrate diet in adults with type 2 diabetes mellitus in India

Purpose

South Asians, especially Indians, face higher diabetes-related risks despite lower body mass index (BMI) compared with the White population. Limited research connects low-carbohydrate high-fat (LCHF)/ketogenic diets to metabolic changes in this group. Systematic studies are needed to assess the long-term effects of the diet, such as ocular health.

Method

In this prospective, observational study, 465 candidates aged 25-75 years with type 2 diabetes included with institutional ethics approval. A total of 119 subjects were included in the final study assessment based on the availability of pathophysiological reports, tears, and blood samples collected at baseline, 3rd, and 6th months. Serum and tear samples were analyzed by an enzyme-linked lectinsorbent assay, to examine secreted soluble protein biomarkers, such as IL-1β (interleukin 1 Beta), IL-6 (interleukin 6), IL-10 (interleukin 10), IL-17A (interleukin 17A), MMP-9 (matrix metalloproteinase 9), ICAM-1 (intercellular adhesion molecule 1), VEGF-A (vascular endothelial growth factor A), and TNF-α (tumor necrosis factor-alpha). A Wilcoxon test was performed for paired samples. Spearman's correlation was applied to test the strength and direction of the association between tear biomarkers and HbA1c. p-value of < 0.05 was considered significant.

Results

After a 3- and 6-month LCHF intervention, fasting blood sugar decreased by 10% (Δ: -14 mg/dL; p < 0.0001) and 7% (Δ: -8 mg/dL; p < 0.0001), respectively. Glycated hemoglobin A1c levels decreased by 13% (Δ: -1%; p < 0.0001) and 9% (Δ: -0.6%; p < 0.0001). Triglycerides reduced by 22% (Δ: -27 mg/dL; p < 0.0001) and 14% (Δ: -19 mg/dL; p < 0.0001). Total cholesterol reduced by 5.4% (Δ: -10.5 mg/dL; p < 0.003) and 4% (Δ: -7 mg/dL; p < 0.03), while low-density lipoprotein decreased by 10% (Δ: -11.5 mg/dL; p < 0.003) and 9% (Δ: -11 mg/dL; p < 0.002). High-density lipoprotein increased by 11% (Δ: 5 mg/dL; p < 0.0001) and 17% (Δ: 8 mg/dL; p < 0.0001). At the first follow-up, tear proteins such as ICAM-1, IL-17A, and TNF-α decreased by 30% (Δ: -2,739 pg/mL; p < 0.01), 22% (Δ: -4.5 pg/mL; p < 0.02), and 34% (Δ: -0.9 pg/mL; p < 0.002), respectively. At the second follow-up, IL-1β and TNF-α reduced by 41% (Δ: -2.4 pg/mL; p < 0.05) and 34% (Δ: -0.67 pg/mL; p < 0.02). Spearman's correlation between HbA1c and tear analytes was not statistically significant.

Conclusion

The LCHF diet reduces the risk of hyperglycemia and dyslipidemia. Changes in tear fluid protein profiles were observed, but identifying promising candidate biomarkers requires validation in a larger cohort.

Prolactin effects on the pathogenesis of diabetes mellitus

BACKGROUND

Prolactin (PRL) is a pituitary hormone promoting lactation in response to the suckling reflex. Beyond its well-known effects, novel tissue-specific and metabolic functions of PRL are emerging.

AIMS

To dissect PRL as a critical mediator of whole-body gluco-insulinemic sensitivity.

METHODS

PubMed-based search with the following terms 'prolactin', 'glucose metabolism', 'type 2 diabetes mellitus', 'type 1 diabetes mellitus', 'gestational diabetes mellitus' was performed.

DISCUSSION

The identification of the PRL-glucose metabolism network poses the basis for unprecedented avenues of research in the pathogenesis of diabetes mellitus type 1 or 2, as well as of gestational diabetes. In this regard, it is of timely relevance to define properly the homeostatic PRL serum levels since glucose metabolism could be influenced by the circulating amount of the hormone.

RESULTS

This review underscores the basic mechanisms of regulation of pancreatic β-cell functions by PRL and provides a revision of articles which have investigated the connection between PRL unbalancing and diabetes mellitus. Future studies are needed to elucidate the burden and the role of PRL in the regulation of glucose metabolism and determine the specific PRL threshold that may impact the management of diabetes.

CONCLUSION

A careful evaluation and context-driven interpretation of PRL levels (e.g., pregnancy, PRL-secreting pituitary adenomas, drug-related hyper- and hypoprolactinemia) could be critical for the correct screening and management of glucometabolic disorders, such as type 1 or 2 as well as gestational diabetes mellitus.

Dopamine D2 receptor antagonist counteracts hyperglycemia and insulin resistance in diet-induced obese male mice

Obesity leads to insulin resistance (IR) and type 2 diabetes. In humans, low levels of the hormone prolactin (PRL) correlate with IR, adipose tissue (AT) dysfunction, and increased prevalence of T2D. In obese rats, PRL treatment promotes insulin sensitivity and reduces visceral AT adipocyte hypertrophy. Here, we tested whether elevating PRL levels with the prokinetic and antipsychotic drug sulpiride, an antagonist of dopamine D2 receptors, improves metabolism in high fat diet (HFD)-induced obese male mice. Sulpiride treatment (30 days) reduced hyperglycemia, IR, and the serum and pancreatic levels of triglycerides in obese mice, reduced visceral and subcutaneous AT adipocyte hypertrophy, normalized markers of visceral AT function (PRL receptor, Glut4, insulin receptor and Hif-1α), and increased glycogen stores in skeletal muscle. However, the effects of sulpiride reducing hyperglycemia were also observed in obese prolactin receptor null mice. We conclude that sulpiride reduces obesity-induced hyperglycemia by mechanisms that are independent of prolactin/prolactin receptor activity. These findings support the therapeutic potential of sulpiride against metabolic dysfunction in obesity.

Prolactin levels in functional hypothalamic amenorrhea: a retrospective case-control study

PURPOSE

Functional hypothalamic amenorrhea (FHA) is due to hypothalamic dysregulation. Literature lacks data about prolactin in FHA women, although both prolactin levels and FHA are associated with stress. Moreover, polycystic ovarian morphology is common in FHA and there is an association between FHA and polycystic ovary syndrome. Thus, the aim of this study was to assess prolactin levels in FHA patients and controls with a special focus on factors influencing prolactin levels, that could be considered as "sensors" of the hypothalamic-pituitary dysregulation.

METHODS

In a retrospective cohort study, 140 women with clearly defined FHA were compared to 70 healthy, normally ovulating women matched for age. The main outcome parameter was prolactin. Factors associated with prolactin levels > 12 µg/L were tested using a multivariable binary logistic regression model.

RESULTS

The median prolactin level was 11.5 µg/L (interquartile range, IQR 7.5-14.4), which was similar to the control group (median 10.7, IQR 8.3-14.5; p = 0.065). Only two women had hyperprolactinemia (prolactin > 25 µg/L; 1.4%). In a multivariable binary logistic regression model eating disorder (odds ratio, OR 0.206; p = 0.040), excessive exercise (OR 0.280; p = 0.031) and TSH (OR 1.923; p = 0.020) were significantly associated with prolactin levels > 12 µg/L.

CONCLUSION

Women with FHA have similar prolactin levels to healthy age-matched individuals. Eating disorders and excessive exercise where associated with prolactin levels < 12 µg/L, in contrast to TSH.

Prolactin in Polycystic Ovary Syndrome: Metabolic Effects and Therapeutic Prospects

Polycystic ovary syndrome (PCOS) is the most prevalent endocrine and metabolic disorder in premenopausal women, characterized by hyperandrogenism, ovulatory dysfunction, and polycystic ovaries. Patients frequently present comorbidities, including obesity, insulin resistance, and impaired glucose and lipid metabolism. The diverse clinical presentation may mimic various endocrine disorders, making the diagnosis challenging in some clinical circumstances. Prolactin (PRL) is a recommended biomarker in the initial diagnostic workup to rule out hyperprolactinemia (HPRL). The traditional role of PRL is linked to lactation and the reproductive system. Recent research highlights PRL's emerging role in metabolic homeostasis. PRL influences metabolism directly by interacting with the pancreas, liver, hypothalamus, and adipose tissue. Its influence on an individual's metabolism is intricately tied to its serum concentration. While deficient and very high levels of PRL can negatively affect metabolism, intermediate-normal to moderately high levels may promote metabolic health. In women with PCOS, PRL levels may be altered. Research results on different aspects of the relationship between PCOS and the impact of various levels of PRL on metabolic homeostasis are limited and inconsistent. In this narrative literature review, we comprehensively examined data on serum PRL levels in PCOS patients. We investigated the correlation between a favorable metabolic profile and serum PRL levels in this population. Furthermore, we explored the concept of beneficial PRL effects on metabolism and discussed the potential therapeutic application of dopamine agonists in PCOS treatment. Lastly, we emphasized several promising avenues for future research in this field.

Improved Insulin Secretion Response and Beta-cell Function Correlated with Increased Prolactin Levels After Laparoscopic Sleeve Gastrectomy in Morbidly Obese Patients with Acanthosis Nigricans

OBJECTIVE

To explore insulin secretion patterns, β-cell function, and serum prolactin (PRL) concentrations in Chinese morbidly obese patients with Acanthosis nigricans (AN) and their alterations after laparoscopic sleeve gastrectomy (LSG).

METHODS

A total of 138 morbidly obese subjects undergoing LSG were categorized as simple obesity without AN (OB group, n = 55) and obesity with AN (AN group, n = 83). Oral glucose tolerance test (OGTT), PRL, and related metabolic indices were performed pre- and 12 months post-LSG. Insulin secretion patterns were derived from insulin secretion peak time during OGTT: type I (peak at 30 or 60 min) and type II (peak at 120 or 180 min).

RESULTS

Preoperatively, AN group showed significantly higher proportions of type II insulin secretion pattern, fasting insulin (FINS), and homeostatic model assessment of insulin resistance (HOMA-IR) whereas lower oral glucose insulin sensitivity (OGIS), insulinogenic index (IGI), and disposition index (DI) than OB group, which were improved significantly at 12 months postoperatively in both groups, more pronounced in AN group. Intriguingly, serum PRL declined substantially in AN group than OB group at baseline whereas elevated only in the AN group post-LSG. After adjusting for confounding factors, elevated PRL correlated significantly with increased IGI and DI, and decreased HOMA-IR in both genders, as well as increased OGIS in females, which was detected only in the AN group CONCLUSION: Morbidly obese patients with AN presented delayed insulin secretion response, impaired insulin secretion, and β-cell dysfunction, which were significantly improved by LSG and might benefit from elevated PRL.

Dopamine receptor agonists mechanism of actions on glucose lowering and their connections with prolactin actions

Robust experiment evidence suggests that prolactin can enhance beta-cell proliferation and increase insulin secretion and sensitivity. Apart from acting as an endocrine hormone, it also function as an adipokine and act on adipocytes to modulate adipogenesis, lipid metabolism and inflammation. Several cross-sectional epidemiologic studies consistently showed that circulating prolactin levels positive correlated with increased insulin sensitivity, lower glucose and lipid levels, and lower prevalence of T2D and metabolic syndrome. Bromocriptine, a dopamine receptor agonist used to treat prolactinoma, is approved by Food and Drug Administration for treatment in type 2 diabetes mellitus since 2009. Prolactin lowering suppress insulin secretion and decrease insulin sensitivity, therefore dopamine receptor agonists which act at the pituitary to lower serum prolactin levels are expected to impair glucose tolerance. Making it more complicating, studies exploring the glucose-lowering mechanism of bromocriptine and cabergoline have resulted in contradictory results; while some demonstrated actions independently on prolactin status, others showed glucose lowering partly explained by prolactin level. Previous studies showed that a moderate increase in central intraventricular prolactin levels stimulates hypothalamic dopamine with a decreased serum prolactin level and improved glucose metabolism. Additionally, sharp wave-ripples from the hippocampus modulates peripheral glucose level within 10 minutes, providing evidence for a mechanistic link between hypothalamus and blood glucose control. Central insulin in the mesolimbic system have been shown to suppress dopamine levels thus comprising a feedback control loop. Central dopamine and prolactin levels plays a key role in the glucose homeostasis control, and their dysregulation could lead to the pathognomonic central insulin resistance depicted in the “ominous octet”. This review aims to provide an in-depth discussion on the glucose-lowering mechanism of dopamine receptor agonists and on the diverse prolactin and dopamine actions on metabolism targets.

Obesity-derived alterations in the lactating mammary gland: Focus on prolactin

Obesity is a modern pandemic with negative consequences in women's reproductive health. Women with overweight and obesity can develop mammary gland alterations that unable exclusive breastfeeding. Obesity associates with a disturbed lactating mammary gland endocrine environment including a decreased action of the hormone prolactin (PRL), the master regulator of lactation. The PRL receptor and the action of PRL are reduced in the mammary gland of lactating rodents fed an obesogenic diet and are contributing factors to impaired lactation in obesity. Also, treatment with PRL improves milk yield in women with lactation insufficiency. This review focuses on the impact of diet-induced obesity in the lactating mammary gland and how obesity impairs the lactogenic action of PRL. Although obesity alters lactation performance in humans and rodents, the responsible mechanisms have been mainly addressed in rodents.

Lower serum PRL is associated with the development of non-alcoholic fatty liver disease: a retrospective cohort study

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) has become an epidemic worldwide and has been linked to a series of metabolic co-morbidities. Prolactin (PRL) has recently been found to have a negative effect on NAFLD, but a causal relationship is not well-understood. Here we investigated the causative relationship between PRL and NAFLD occurrence.

METHODS

In this retrospective cohort study, we enrolled patients without NAFLD who were diagnosed by abdominal ultrasonography undergone serum PRL testing at 8.00 a.m. at baseline, and followed up for a median of 32 (19, 46) months.

RESULTS

This study enrolled 355 persons [215 men and 140 women; media age 56 (49, 64) years], in which 72 (20.28%) patients who eventually developed NAFLD. Compared with those in the non-NAFLD group, basal serum PRL levels of patients were lower in the NAFLD group [male: 7.35 (5.48, 10.60) vs. 9.13 (6.92, 12.50) ug/L, P = 0.002; female: 5.66 (4.67, 9.03) vs. 9.01 (6.31, 11.60) ug/L, P = 0.009]. The prevalence of NAFLD was significantly decreased along with the increased quartile of basal serum PRL levels in both genders (P < 0.05). Serum PRL concentration was independently associated with NAFLD development [male: OR, 0.881 (0.777, 0.998), P = 0.047; female: OR, 0.725 (0.554, 0.949), P = 0.019].

CONCLUSION

Our study is the first to find that basal serum PRL level can predict the occurrence of NAFLD and it may be a potential biomarker to prevent and treat NAFLD.

The metabolic role of prolactin: systematic review, meta-analysis and preclinical considerations

INTRODUCTION

Hyperprolactinemia has been proven to induce hypogonadism and metabolic derangements in both genders, while the consequences of prolactin (PRL) deficiency have been poorly investigated.

AREAS COVERED

To systematically review and analyze data from clinical studies focusing on the metabolic consequences of abnormally high prolactin levels (HPRL) and low prolactin levels (LPRL). In addition, data from preclinical studies about underlying pathophysiological mechanisms were summarized and discussed.

EXPERT OPINION

PRL contributes to providing the correct amount of energy to support the mother and the fetus/offspring during pregnancy and lactation, but it also has a homeostatic role. Pathological PRL elevation beyond these physiological conditions, but also its reduction, impairs metabolism and body composition in both genders, increasing the risk of diabetes and cardiovascular events. Hence, hypoprolactinemia should be avoided as much as possible during treatment with dopamine agonists for prolactinomas. Patients with hypoprolactinemia, because of endogenous or iatrogenic conditions, deserve, as those with hyperprolactinemia, careful metabolic assessment.

Hormone supply to the pituitary gland: A comprehensive investigation of female‑related tumors (Review)

The hypothalamus acts on the pituitary gland after signal integration, thus regulating various physiological functions of the body. The pituitary gland includes the adenohypophysis and neurohypophysis, which differ in structure and function. The hypothalamus-hypophysis axis controls the secretion of adenohypophyseal hormones through the pituitary portal vein system. Thyroid-stimulating hormone, adrenocorticotropic hormone, gonadotropin, growth hormone (GH), and prolactin (PRL) are secreted by the adenohypophysis and regulate the functions of the body in physiological and pathological conditions. The aim of this review was to summarize the functions of female-associated hormones (GH, PRL, luteinizing hormone, and follicle-stimulating hormone) in tumors. Their pathophysiology was described and the mechanisms underlying female hormone-related diseases were investigated.

Ketogenic Diet Benefits to Weight Loss, Glycemic Control, and Lipid Profiles in Overweight Patients with Type 2 Diabetes Mellitus: A Meta-Analysis of Randomized Controlled Trails

A ketogenic diet, characterized by low calories with high levels of fat, adequate levels of protein, and low levels of carbohydrates, has beneficial effects on body weight control in overweight patients. In the present study, a meta-analysis was conducted to investigate the role of a ketogenic diet in body weight control and glycemic management in overweight patients with type 2 diabetes mellitus (T2DM). In summary, we systematically reviewed articles from the Embase, PubMed, Web of Science and Cochrane Library databases and obtained eight randomized controlled trials for meta-analysis. The results show that a ketogenic diet had significantly beneficial effects on the loss of body weight (SMD, -5.63, p = 0.008), the reduction of waist circumference (SMD, -2.32, p = 0.04), lowering glycated hemoglobin (SMD, -0.38, p = 0.0008) and triglycerides (SMD, -0.36, p = 0.0001), and increasing high-density lipoproteins (SMD, 0.28, p = 0.003). Overall, these results suggest that a ketogenic diet may be an effective dietary intervention for body weight and glycemic control, as well as improved lipid profiles in overweight patients with T2DM. Hence, a ketogenic diet can be recommended for the therapeutic intervention of overweight patients with T2DM.

Association of Serum Prolactin With Type 2 Diabetes Mellitus: A Comparative Cross-Sectional Study From South India

BACKGROUND

 The association of serum prolactin (PRL) with diabetes is still uncertain, with a paucity of data in the south Indian population. This study aims to compare the serum PRL levels between type 2 diabetes mellitus (T2DM) patients and normoglycaemic volunteers and correlate the serum PRL level with fasting plasma glucose (FPG), postprandial plasma glucose (PPG), glycated haemoglobin (HbA1c) levels, and the lipid profile in the study population.

METHODS

 This was a comparative cross-sectional study among 112 T2DM participants and 112 healthy volunteers in a tertiary care centre in India. All participants were tested for FPG, PPG, HbA1c, fasting serum lipid profile, and serum PRL, which were compared between T2DM patients and healthy volunteers.

RESULTS

 The serum PRL in T2DM patients was significantly lower compared to healthy volunteers (8.67 ± 4.37 vs. 13.76 ± 6.55 ng/ml, P < 0.001). FPG, PPG, and HbA1c correlated inversely with serum PRL in our study population. On multivariable logistic regression adjusted for age and sex, a higher serum PRL level within the physiological range was protective for T2DM (adjusted odds ratio: 0.83, 95% CI: 0.77-0.90, P < 0.001). Serum PRL levels were inversely correlated with serum total cholesterol, low-density lipoprotein cholesterol, and triglycerides, but not with high-density lipoprotein cholesterol.

CONCLUSIONS

A high serum PRL within the physiological range was inversely associated with the prevalence of T2DM in the south Indian population. Serum PRL also correlated inversely with glycaemic and blood lipid parameters. Larger longitudinal studies are required to further validate the association of serum PRL with various components of metabolic syndrome in the south Indian population.

The beneficial metabolic actions of prolactin

The role of prolactin (PRL) favoring metabolic homeostasis is supported by multiple preclinical and clinical studies. PRL levels are key to explaining the direction of its actions. In contrast with the negative outcomes associated with very high (>100 μg/L) and very low (<7 μg/L) PRL levels, moderately high PRL levels, both within but also above the classically considered physiological range are beneficial for metabolism and have been defined as HomeoFIT-PRL. In animal models, HomeoFIT-PRL levels counteract insulin resistance, glucose intolerance, adipose tissue hypertrophy and fatty liver; and in humans associate with reduced prevalence of insulin resistance, fatty liver, glucose intolerance, metabolic syndrome, reduced adipocyte hypertrophy, and protection from type 2 diabetes development. The beneficial actions of PRL can be explained by its positive effects on main metabolic organs including the pancreas, liver, adipose tissue, and hypothalamus. Here, we briefly review work supporting PRL as a promoter of metabolic homeostasis in rodents and humans, the PRL levels associated with metabolic protection, and the proposed mechanisms involved. Finally, we discuss the possibility of using drugs elevating PRL for the treatment of metabolic diseases.

The Effect of Leptin on the Regulation of Immune Responses in Women with Polycystic Ovary Syndrome

&lt;b&gt;Background and Objective:&lt;/b&gt; Leptin is a hormone produced by fat cells in adipose tissue that plays a biological role in metabolism, immune system control and energy flow regulation. The study's objective was to investigate serum leptin levels in PCOS females and determine how they are related to immunological and hormonal parameters. &lt;b&gt;Materials and Methods:&lt;/b&gt; Thirty PCOS women were chosen for the study and compared to thirty healthy women as control samples, with both case and normal samples ranging in age from 18-36 years. WBC count, absolute numbers of neutrophils, lymphocytes, monocytes, eosinophils, leptin, Prolactin and serum IgA levels were measured. &lt;b&gt;Results:&lt;/b&gt; The results showed the mean WBC, lymphocytes and eosinophil absolute numbers in PCOS women were significantly different. However, there was no significant difference in the absolute numbers of neutrophils and monocytes. The findings also revealed a significant increase in BMI, IgA, leptin and prolactin levels in PCOS when compared to controls. The results showed strong positive correlation coefficients between BMI and IgA (1.000**), WBC with neutrophils, lymphocytes and monocytes (0.797**, 0.790**, 0.712**), respectively and finally leptin and prolactin (0.474**). The same test, on the other hand, revealed an inverse correlation coefficient between BMI, IgA and prolactin (-0.376*, -0.376*, respectively with p&lt;u&gt;<&lt;/u&gt;0.05). &lt;b&gt;Conclusion:&lt;/b&gt; A rise in the levels of the hormones leptin and prolactin, which were positively associated with the body mass index in women with PCOS, was found in the current study. The findings revealed that the hormones leptin and prolactin have an effect on some immune parameters in women with PCOS.

J-Shaped Relationship Between Serum Prolactin and Metabolic-Associated Fatty Liver Disease in Female Patients With Type 2 Diabetes

BACKGROUND

Metabolic-associated fatty liver disease (MAFLD) has become a worldwide epidemic. Prolactin (PRL), a pituitary hormone, has been linked to MAFLD. As a result, we set out to look into the relationship between serum PRL and the risk of MAFLD in patients with type 2 diabetes mellitus (T2DM).

METHODS

A total of 724 adults with T2DM were enrolled and categorized as MAFLD and non-MAFLD groups. Anthropometric data, biochemical parameters, and serum PRL levels were collected. Liver steatosis and fibrosis were assessed using FibroScan. Patients were stratified into normal PRL (NP) and high PRL (HP) groups and divided into four groups based on serum PRL quartiles. Multivariate logistic regression analysis was performed to evaluate the association between serum PRL and MAFLD risk.

RESULTS

Female but not male patients with MAFLD, liver steatosis, and fibrosis had significantly lower PRL levels in the NP group but higher PRL levels in the HP group than their counterparts. The proportions of MAFLD, liver steatosis, and fibrosis were significantly decreased in the NP group but increased in the HP group across the PRL quartiles in females but not in males. After multivariate adjustment, the adjusted ORs (AORs) and 95% CI for MAFLD among females were 18.165 (3.425-96.336), 1.784 (0.658-5.002), 1.744 (0.608-4.832), and 1.00 (reference) in the NP group (Q1-Q4, P-trend < 0.001) and 1.00 (reference), 11.098 (1.819-110.356), 15.225 (1.996-116.112), and 18.211 (2.579-128.568) in the HP group (Q1-Q4, P-trend = 0.020). Such associations were also found between serum PRL and liver fibrosis in females but not in males.

CONCLUSION

We observed a J-shaped association between serum PRL and the risk of MAFLD and liver fibrosis in females but not in males with T2DM, indicating that PRL may be relevant to MAFLD and its progression in a gender-specific manner.

CLINICAL TRIAL REGISTRATION

Chinese Clinical Trial Registry, number ChiCTR-OCS-12002381.

Severe Hyperprolactinemia Promotes Brown Adipose Tissue Whitening and Aggravates High Fat Diet Induced Metabolic Imbalance

BACKGROUND

The association of high serum prolactin and increased body weight is positive but controversial, therefore we hypothesized that additional factors such as diets and the impact of prolactin on brown adipose tissue may condition its metabolic effects.

METHODS

We used LacDrd2KO females with lifelong severe hyperprolactinemia due dopamine-D2 receptor deletion from lactotropes, and slow onset of metabolic disturbances, and compared them to their respective controls (Drd2 ^loxP/loxP ). Food intake, and binge eating was evaluated. We then challenged mice with a High Fat (HFD) or a Control Diet (CD) for 8 weeks, beginning at 3 months of age, when no differences in body weight are found between genotypes. At the end of the protocol brown and white adipose tissues were weighed, and thermogenic and lipogenic markers studied, using real time PCR (Ucp1, Cidea, Pgc1a, Lpl, adiponectin, Prlr) or immunohistochemistry (UCP1). Histochemical analysis of brown adipose tissue, and glucose tolerance tests were performed.

RESULTS

Hyperprolactinemic mice had increased food intake and binge eating behavior. Metabolic effects induced by a HFD were exacerbated in lacDrd2KO mice. Hyperprolactinemia aggravated HFD-induced body weight gain and glucose intolerance. In brown adipose tissue pronounced cellular whitening as well as decreased expression of the thermogenic markers Ucp1 and Pgc1a were observed in response to high prolactin levels, regardless of the diet, and furthermore, hyperprolactinemia potentiated the decrease in Cidea mRNA expression induced by HFD. In subcutaneous white adipose tissue hyperprolactinemia synergistically increased tissue weight, while decreasing Prlr, Adiponectin and Lpl mRNA levels regardless of the diet.

CONCLUSIONS

Pathological hyperprolactinemia has a strong impact in brown adipose tissue, lowering thermogenic markers and evoking tissue whitening. Furthermore, it modifies lipogenic markers in subcutaneous white adipose, and aggravates HFD-induced glucose intolerance and Cidea decrease. Therefore, severe high prolactin levels may target BAT function, and furthermore represent an adjuvant player in the development of obesity induced by high fat diets.

Metabolic effects of prolactin and the role of dopamine agonists: A review

Prolactin is a polypeptide hormone that is well known for its role in reproductive physiology. Recent studies highlight its role in neurohormonal appetite regulation and metabolism. Elevated prolactin levels are widely associated with worsening metabolic disease, but it appears that low prolactin levels could also be metabolically unfavorable. This review discusses the pathophysiology of prolactin related metabolic changes, and the less commonly recognized effects of prolactin on adipose tissue, pancreas, liver, and small bowel. Furthermore, the effect of dopamine agonists on the metabolic profiles of patients with hyperprolactinemia are discussed as well.

Circulating prolactin level is increased in metabolically healthy obesity

OBJECTIVE

Prolactin (PRL) has been demonstrated as a metabolic hormone to regulate energy metabolism recently. The present study aims to investigate the association between PRL and metabolic alterations in different obesity phenotypes.

METHODS

A total of 451 drug-naive participants were recruited, comprising 351 obese patients and 100 age- and sex-matched healthy participants with normal weight. PRL, anthropometric, and clinical parameters were measured.

RESULTS

In the obesity group, 15.1% (53/351) were categorized as 'metabolically healthy obesity (MHO)'. Besides favorable blood pressure, glucose, and lipids profiles, the MHO group exhibited increased PRL, and lower levels of high-sensitivity C-reactive protein (hsCRP), homeostasis model assessment of insulin resistance (HOMA-IR), and adipose tissue insulin resistance (adipo-IR) than the metabolically unhealthy obesity (MUHO) group (PRL, HOMA-IR, and adipo-IR: P < 0.01; hsCRP: P < 0.05). The severe MUHO group showed significantly decreased PRL levels than the mild MUHO group (P < 0.05). Multivariate linear regression analysis indicated that fasting plasma glucose (FBG) and adipo-IR were significantly associated with PRL (FBG: β = -0.263, P < 0.05; adipo-IR: β = -0.464, P < 0.01). Multivariable logistic regression analysis showed that hsCRP (OR = 0.824) and PRL (OR = 1.211) were independent predictors of MHO (all P < 0.01).

CONCLUSION

The MHO group had significantly increased circulating PRL levels when compared with the control and MUHO groups, and multivariable logistic regression analysis showed that PRL was independent predictors of MHO. Our findings suggested that increased circulating PRL might be a compensatory response for favoring energy metabolism during obesity.

Increased Prolactin is an Adaptive Response to Protect Against Metabolic Disorders in Obesity

OBJECTIVE

Prolactin (PRL) is a polypeptide hormone named for its crucial role in lactation. Recently, PRL has been recognized as a metabolic hormone that regulates energy metabolism. The current study aimed to investigate the relationship between circulating PRL and metabolic alterations in overweight/obese patients and the effect of weight loss through bariatric surgery on circulating PRL.

METHODS

A total of 448 overweight/obese patients aged between 18 and 40 years and 120 age- and sex-matched healthy controls with normal weight were enrolled. Among all participants, 156 obese patients underwent bariatric surgery.

RESULTS

Circulating PRL levels were significantly increased in the overweight (15.27 ± 9.58 μg/L) and obese (17.75 ± 9.15 μg/L) groups compared with the normal weight (13.57 ± 9.03 μg/L) group. Multiple regression analyses demonstrated that the adipose tissue insulin resistance (adipo-IR) level was an independent predictor for PRL (β = -0.451, P < .01). Despite comparable anthropometric parameters, the overweight/obese patients with a higher PRL tertile had decreased levels of triglycerides, nonesterified fatty acids, homeostasis model assessment of insulin resistance, and adipo-IR compared with the patients in the moderate and lower PRL tertiles. Serum PRL levels were significantly decreased following the alleviation of metabolic parameters after bariatric surgery (from 17.12 ± 8.27 to 13.00 ± 5.78 μg/L, P < .05), and the decrease in PRL levels was significantly greater in the lower adipo-IR group than in the higher adipo-IR group (P < .01).

CONCLUSION

An increased serum PRL level might be an adaptive response for protecting against metabolic disorders in obesity.

Effect of the ketogenic diet on glycemic control, insulin resistance, and lipid metabolism in patients with T2DM: a systematic review and meta-analysis

Background

At present, the beneficial effect of the ketogenic diet (KD) on weight loss in obese patients is generally recognized. However, a systematic research on the role of KD in the improvement of glycemic and lipid metabolism of patients with diabetes is still found scarce.

Methods

This meta-study employed the meta-analysis model of random effects or of fixed effects to analyze the average difference before and after KD and the corresponding 95% CI, thereby evaluating the effect of KD on T2DM.

Results

After KD intervention, in terms of glycemic control, the level of fasting blood glucose decreased by 1.29 mmol/L (95% CI: −1.78 to −0.79) on average, and glycated hemoglobin A1c by 1.07 (95% CI: −1.37 to −0.78). As for lipid metabolism, triglyceride was decreased by 0.72 (95% CI: −1.01 to −0.43) on average, total cholesterol by 0.33 (95% CI: −0.66 to −0.01), and low-density lipoprotein by 0.05 (95% CI: −0.25 to −0.15); yet, high-density lipoprotein increased by 0.14 (95% CI: 0.03−0.25). In addition, patients’ weight decreased by 8.66 (95% CI: −11.40 to −5.92), waist circumference by 9.17 (95% CI: −10.67 to −7.66), and BMI by 3.13 (95% CI: −3.31 to −2.95).

Conclusion

KD not only has a therapeutic effect on glycemic and lipid control among patients with T2DM but also significantly contributes to their weight loss.

Metabolic functions of prolactin: Physiological and pathological aspects

Prolactin is named after its vital role of promoting milk production during lactation, although it has been implicated in multiple functions within the body, including metabolism and energy homeostasis. Prolactin has been hypothesised to play a key role in driving many of the adaptations of the maternal body to allow the mother to meet the physiological demands of both pregnancy and lactation, including the high energetic demands of the growing foetus followed by milk production to support the offspring after birth. Prolactin receptors are found in many tissues involved in metabolism and food intake, such as the pancreas, liver, hypothalamus, small intestine and adipose tissue. We review the literature examining the effects of prolactin in these various tissues and how they relate to changes in function in physiological states of high prolactin, such as pregnancy and lactation, and in pathological states of hyperprolactinaemia in the adult. In many cases, whether prolactin promotes healthy metabolism or leads to dysregulation of metabolic functions is highly dependent on the situation. Overall, although prolactin may not play a major role in regulating metabolism and body weight outside of pregnancy and lactation, it definitely has the ability to contribute to metabolic function.

Association between variations of physiological prolactin serum levels and the risk of type 2 diabetes: A systematic review and meta-analysis

AIM

To determine the pooled association between variations of prolactin serum levels within the physiological range and the risk of type 2 diabetes mellitus (T2D).

METHODS

Pubmed, Scopus, Web of Science, and grey literature were searched for studies investigating the association between variations of prolactin serum levels in the normal range and the risk of T2D in adults. The risk of prevalent and incident T2D was summarized as the odds ratio or relative risk according to the quartile of prolactin serum concentration, using random-effects meta-analysis.

RESULTS

Of 2,014 articles identified, 6 met the inclusion criteria. Data were pooled from cross-sectional studies including 6,670 subjects and longitudinal studies involving 13,203 subjects. Men with prolactin levels in the fourth quartile versus those in the first quartile had decreased risk of prevalent T2D (OR 0.52; 95%CI 0.35-077). The same association was seen in women (OR 0.46; 95%CI 0.30-0.73). Conversely, prolactin levels in the fourth versus first quartile were not associated with the risk of incident T2D in men (RR 1.21; 95%CI 0.79-1.87) or women (RR 0.77; 95%CI 0.48-1.22).

CONCLUSION

Higher prolactin serum levels within the normal range were associated with reduced risk of prevalent but not incident T2D. Further studies are necessary to address whether this association is causal, but these findings raise the discussion regarding the optimal level of prolactin suppression in subjects undergoing therapy with dopaminergic agonists.

Glucose-Lipid Metabolism in Obesity with Elevated Prolactin Levels and Alteration of Prolactin Levels After Laparoscopic Sleeve Gastrectomy

PURPOSE

We investigated the differences in metabolism between obesity with or without increased prolactin (PRL) and the change in PRL after laparoscopic sleeve gastrectomy (LSG).

METHODS

Patients were divided into two groups: obesity with normal PRL (NP, n = 123) and high PRL (HP, n = 108). Glucose-lipid metabolism and inflammation were measured. A total of 115 patients with obesity (NP, n = 64; HP, n = 51) underwent LSG were recruited, and PRL was measured at 12 months after LSG.

RESULTS

(1) Blood glucose (BG), total cholesterol (TCH), LDL, triglyceride, and TNF-α were lower in the HP than in the NP group in the cross-sectional study (all P < 0.05). (2) PRL was negatively associated with neck circumference, waist-to-hip ratio, systolic blood pressure, heart rate, basal metabolism rate (BMR), ALP, TCH, and LDL in all subjects. PRL levels were positively associated with weight, HC, and BMR in males but were negatively associated with ALT, AST, ALP, BG 30 min, BG 60 min, FFA, and TCH in females (all P < 0.05). (3) Regression analysis showed that PRL negatively correlated with ALP and LDL-C in the whole baseline (β = - 0.051, P = 0.002; β = - 1.372, P = 0.033). PRL was a negative factor for ALP in females and a positive factor for BMR2 in males (β = - 0.099, P = 0.041; β = 0.005, P = 0.006). (4) PRL decreased in the HP group and increased in the NP group at 12 months post-operation (all P < 0.05). Increased PRL was associated with a change in TCH in the NP group (P < 0.05).

CONCLUSION

Increased PRL resulted in improved glucose-lipid metabolism and chronic low-grade inflammation. LSG led to increased PRL in NP and decreased PRL in HP. Improved lipid was associated with increased PRL in NP after surgery.

CLINICAL TRIAL REGISTRATION NUMBER

ChiCTR-OCS-12002381.

The Association Between Prolactin and Metabolic Parameters in PCOS Women: A Retrospective Analysis

Background: The aim of this retrospective study was to analyze the association between prolactin (PRL) and metabolic parameters in infertile patients with polycystic ovary syndrome (PCOS). Methods: A total of 2,052 patients with PCOS and 9,696 patients with tubal infertility (non-PCOS) undergoing in vitro fertilization and embryo transfer (IVF-ET) at the reproductive medicine center of the first affiliated hospital of Wenzhou Medical University from January 2007 to July 2017 were enrolled in this study. Serum PRL, basic endocrine hormones, fasting plasma lipid, fasting plasma glucose (FPG), liver function, thyroid hormone and other parameters were measured and analyzed. Result: PRL levels were significantly lower in PCOS patients than controls over all age groups (p < 0.05). In the PCOS patients, serum PRL was significantly and positively correlated with FPG, serum TSH and serum FT4, and significantly and negatively correlated with LH, LH/FSH, TC, TG, LDL-C, AST, ALT, γ-GGT, FT3, and FT3/FT4 (p < 0.05 or 0.01). After adjusted for age and body mass index (BMI), serum PRL was positively correlated with FPG, TSH, and FT4, and negatively correlated with LH and LH/FSH. Conclusion: Low serum PRL may be an important cause of metabolic risk in infertile patients with PCOS.