Prolactin does not seem to mediate the improvement on insulin resistance markers and blood glucose levels related to breastfeeding

Introduction

The prevalence of type 2 diabetes mellitus (T2DM) is increasing worldwide. Strategies to decrease this risk should be strongly encouraged. Lactation has been associated, for the mother, with reduction in future T2DM risk in several studies. The mechanisms behind this phenomenon, however, are poorly understood. The aims of this study were, first, to compare blood glucose levels and markers of insulin resistance (MIR) in early postpartum women with overweight/obesity according to their breastfeeding status and, second, to evaluate whether prolactin (PRL) levels could mediate improvements in these parameters.

Methods

The prospective study followed 95 women older than 18 years from early pregnancy for up to 60 to 180 days postpartum. All participants had a BMI > 25 kg/m2 and a singleton pregnancy. At each visit, questionnaires and clinical and biochemical evaluations were performed. Participants were divided into two groups according to the breastfeeding status as "yes" for exclusive or predominant breastfeeding, and "no" for not breastfeeding.

Results

Breastfeeding women (n = 44) had significantly higher PRL levels [47.8 (29.6-88.2) vs. 20.0 (12.0-33.8), p< 0.001]. They also had significantly lower fasting blood glucose levels [89.0 (8.0) vs. 93.9 (12.6) mg/dl, p = 0.04], triglycerides (TG) [92.2 (37.9) vs. 122.4 (64.4) mg/dl, p = 0.01], TG/HDL ratio [1.8 (0.8) vs. 2.4 (1.6) mg/dl, p = 0.02], TyG index [8.24 (0.4) vs. 8.52 (0.53), p = 0.005], fasting serum insulin [8.9 (6.3-11.6) vs. 11.4 (7.7-17.0), p = 0.048], and HOMA-IR [2.0 (1.3-2.7) vs. 2.6 (1.6-3.9), p = 0.025] in the postpartum period compared to the non-breastfeeding group. Groups were homogeneous in relation to prevalence of GDM, pre-gestational BMI, as well as daily caloric intake, physical activity, and weight loss at postpartum. Linear regression analysis with adjustments for confounders showed a statistically significant association of breastfeeding with fasting blood glucose [-6.37 (-10.91 to -1.83), p = 0.006], HOMA-IR [-0.27 (-0.51 to -0.04), p = 0.024], TyG index [-0.04 (-0.06 to -0.02), p = 0.001], and TG/HDL ratio [-0.25 (-0.48 to -0.01), p = 0.038]. Mediation analysis showed that PRL did not mediate these effects. Sensitivity analyses considering different cutoffs for PRL levels also did not show modification effect in the mediation analyses.

Conclusion

Breastfeeding was associated with improvement in glucose metabolism and MIR 60 to 180 days after birth in overweight and obese women, even when adjusted for confounders. PRL levels were not found to mediate the association between breastfeeding and improvement in MIR.

Gender Disparities in Prolactinomas: Unravelling Clinical Patterns, Metabolic Variations, and Treatment Responses

Background and objective Individuals with prolactinoma exhibit elevated rates of obesity, metabolic syndrome (MS), and dyslipidemia compared to their healthy counterparts. However, there is a lack of data regarding metabolic variance between male and female prolactinoma patients. Consequently, this study aimed to investigate and compare sex-specific discrepancies in metabolic abnormalities among individuals diagnosed with prolactinoma. Methods In this prospective study, 80 treatment-naïve patients with prolactinoma (12 males and 68 females) underwent clinical assessments and laboratory investigations. The measured parameters included blood glucose, total cholesterol (TC), triglycerides (TG), LDL cholesterol (LDL-C), HDL cholesterol (HDL-C), urea, creatinine, uric acid, and blood glucose levels. The patients were treated with cabergoline, a dopamine agonist, and reevaluated after 12 weeks. Results Forty-eight patients had microprolactinomas (all females), and 32 had macroprolactinomas (20 females, 12 males). The mean age was 28.30±7.49 years for females and 28.91±7.12 years for males (p=0.71). The median symptom duration was 12 months (range 1-72 months, IQR 4-16 months), with no significant difference between males (median 12 months, IQR 5-54 months) and females (median 12 months, IQR 10-24 months, p=0.620). The median serum prolactin (PRL) was 988 ng/mL (IQR 471-1,439) in males and 165 ng/mL (IQR 90-425) in females (p<0.05). Males showed higher HbA1c, BGF, TC, TG, LDL-C, and higher rates of obesity, MS, and diabetes mellitus. Treatment with cabergoline resulted in significant improvements in the HbA1c, BGF, TC, TG, and LDL-C levels. Conclusion Males with prolactinomas had larger tumor sizes and higher serum PRL levels than females. Additionally, males exhibited worse metabolic parameters than females. However, there was no significant difference in the duration of symptoms or age at diagnosis between the two groups.

Case report on gynecomastia with ipsilateral recurrence of granulomatous lobular mastitis

This study describes a rare case of male granulomatous lobular mastitis (GLM) with recurrence in different sites on the ipsilateral side. A 48-year-old male patient presented with no previous history of breast-related disease, and physical examination suggested a mass in the right breast. Ultrasonography revealed a cyst and infection in the right breast. No obvious abnormality was found in laboratory analysis, and a core needle biopsy revealed GLM. Incision and drainage were applied to the right lesion, and symptoms resolved within a few weeks. At 2 years following this initial presentation, the patient reported that the right breast mass reappeared in different locations after the consumption of alcohol. Relevant examination and a core needle biopsy again suggested GLM of the right breast. The patient declined hormone therapy and was subsequently lost to follow-up. After reviewing this case, the course of the disease in this patient, and the connection between gynecomastia and GLM, along with ipsilateral recurrence, are under investigation.

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.

A scoping review to understand the indications, effectiveness, and limitations of cabergoline in radiological and biochemical remission of prolactinomas

Cabergoline has long been used in the medical management of prolactin-secreting pituitary adenomas. However, there is contradicting and inadequate evidence on the efficacy of cabergoline in achieving radiological and biochemical remission in prolactinoma. This article presents scoping review of evidence in cabergoline achieving radiological and biochemical remission in cases of prolactinoma. We have used a recommended scoping review methodology to map and summarize existing research evidence and identify knowledge gaps. The review process was conducted according to the PRISMA-ScR guidelines (Preferred Reporting Items for Systematic reviews and Meta-Analyses Extension for Scoping Reviews). The selection of studies was based on the criteria defined. Essential information such as reference details, study characteristics, topics of interest, main findings, and the study author's conclusion are presented in text and tables. With the study selection process, eight publications were finally included-one systematic review and meta-analysis, one RCT, and six primary studies. Cabergoline is effective in achieving biochemical and radiological remission in cases of prolactinoma. We identified several knowledge gaps with the scoping review and directions for future studies. Future studies, including randomized studies, will help address challenging questions associated with the management of prolactinoma.

Time for a New Perspective on Prolactin in Metabolism

The pituitary hormone prolactin (PRL) regulates a variety of functions beyond reproduction. The association between physiological (pregnancy) and pathological (prolactinoma) hyperprolactinemia and metabolic alterations led to the concept of this hormone being diabetogenic. However, large cohort clinical studies have recently shown that low circulating PRL levels are associated with metabolic disease and represent a risk factor for type 2 diabetes (T2D), whereas high PRL levels are beneficial. Moreover, PRL acts on the pancreas, liver, adipose tissue, and hypothalamus to maintain and promote metabolic homeostasis. By integrating basic and clinical evidence, we hypothesize that upregulation of PRL levels is a mechanism to maintain metabolic homeostasis and, thus, propose that the range of PRL levels considered physiological should be expanded to higher values.

Circulating prolactin and breast cancer risk among pre- and postmenopausal women in the EPIC cohort

BACKGROUND

Experimental and epidemiological evidence suggests that prolactin might play a role in the etiology of breast cancer. We analyzed the relationship of prediagnostic circulating prolactin levels with the risk of breast cancer by menopausal status, use of postmenopausal hormone replacement therapy (HRT) at blood donation, and by estrogen and progesterone receptor status of the breast tumors.

PATIENTS AND METHODS

Conditional logistic regression was used to analyze the data from a case-control study nested within the prospective European EPIC cohort, including 2250 invasive breast cancer and their matched control subjects.

RESULTS

Statistically significant heterogeneity in the association of prolactin levels with breast cancer risk between women who were either pre- or postmenopausal at the time of blood donation was observed (Phet = 0.04). Higher serum levels of prolactin were associated with significant increase in the risk of breast cancer among postmenopausal women [odds ratio (OR)Q4-Q1 = 1.29 (95% confidence interval, CI, 1.05-1.58), Ptrend = 0.09]; however, this increase in risk seemed to be confined to women who used postmenopausal HRT at blood donation [ORQ4-Q1 = 1.45 (95% CI 1.08-1.95), Ptrend = 0.01], whereas no statistically significant association was found for the non-users of HRT [ORQ4-Q1 = 1.11 (95%CI 0.83-1.49), Ptrend = 0.80] (Phet = 0.08). Among premenopausal women, a statistically non-significant inverse association was observed [ORQ4-Q1 = 0.70 (95% CI 0.48-1.03), Ptrend = 0.16]. There was no heterogeneity in the prolactin-breast cancer association by hormone receptor status of the tumor.

CONCLUSION

Our study indicates that higher circulating levels of prolactin among the postmenopausal HRT users at baseline may be associated with increased breast cancer risk.