Reviews in Endocrine & Metabolic Disorders最新文献

This paper provides a critical overview on GHRH and its deficiency, discussing its multiple roles in both central and peripheral tissues. Genetically engineered mice have been instrumental in elucidating the multifaceted roles of GHRH and GH, each offering unique insights into the physiological and pathological roles of these hormones, although in many of these models dissecting the direct effect of GHRH from the effect of GH is not possible. Key findings highlight the effects of GHRH deficiency on emotional behavior, including anxiety and depression, its impact on memory and learning capabilities, as well as on adipose tissue, immune system, inflammation and pain.

Growth hormone (GH) secretion is pulsatile, entropic, and nycthemeral and is mainly controlled by the hypothalamus through two neurohormones, the stimulating growth hormone releasing hormone (GHRH) and the inhibiting somatostatin. Shortly after its discovery and synthesis, GHRH was intensely investigated diagnostically to define GH secretion. The nascent enthusiasm for using GHRH as a single diagnostic tool to investigate GH deficiency (GHD) dropped down quickly due to a flawed reproducibility. The subsequent combinatory use of molecules implicated in GH secretion through inhibition of the somatostatinergic tone, such as arginine (ARG), or the synthesis of receptor-orphan pharmaceutical compounds capable of stimulating pituitary somatotrophs to release GH, such as the GH secretagogues (GHSs), improved the reproducibility of GH response to GHRH alone, thus gaining access into the clinical practice by means of different diagnostic approaches. This review will focus on the history of the GHRH test, with main emphasis on GHRH plus ARG as a dynamic testing for the diagnosis of GHD. Our attention will extend crosswise from studies aimed at validating GHRH-based tests for the clinical practice, to address main pitfall conditions capable of affecting per se GH secretion, such as obesity, hypothalamic damage, and ageing. The history of GHRH test has been progressively dismantled due to the cease of its production for business reasons, opening a gap in the diagnostic workup of patients with GHD. In the urgency to seek further robust, safe, and validated diagnostic tests or tools, we hope to stimulate attention on a so important peptide for the health of our patients suffering from pituitary diseases.

Neuroendocrine neoplasms (NENs) originating in the gastroenteropancreatic (GEP) tract are rare tumors often associated with significant metabolic disturbances and nutritional challenges. This review explores the intricate relationship between nutritional status and the development, progression, and prognosis of GEP-NENs. Through an extensive literature search encompassing studies up to April 2024, we examined various factors, including obesity, malnutrition, metabolic syndrome and type 2 diabetes mellitus, and their roles in the development and progression of GEP-NENs. The review highlights the dual role of obesity, both as a risk factor and a potential prognostic indicator, drawing attention to the 'obesity paradox' observed in cancer research. Additionally, we discuss the impact of malnutrition on patient outcomes and emphasize the need for comprehensive nutritional assessments beyond BMI. This analysis highlights the importance of incorporating nutritional interventions into preventive and therapeutic strategies for GEP-NEN patients. Future research should further clarify these associations and develop personalized nutritional management protocols to improve patient prognosis and quality of life. Acronyms adopted in the text and tables: AOR: adjusted odd ratio, BIA: Bioelectrical Impedance Analysis, BMI: Body Mass Index, CI: confidence interval, CLARINET: Controlled Study of Lanreotide Antiproliferative Response in Neuroendocrine Tumor, FLI: fatty liver index, GEP: gastroenteropancreatic, GLIM: global leadership into malnutrition, HR: hazard ratio, MS: metabolic syndrome, MUST: malabsorption universal screening tool, NEC: neuroendocrine carcinoma, NENs: Neuroendocrine neoplasms, NETs: Neuroendocrine tumors, NRS: Nutritional Risk Screening, OR: odd ratio, OS: overall survival, PFS: progression-free survival, RR: risk ratio, SGA: Subjective Global Assessment, T2DM: type 2 diabetes mellitus, VAI: visceral adiposity index, WD: well-differentiated.

Prolactin deficiency is rare. It generally occurs when pituitary disorders, such as large pituitary tumors, pituitary apoplexy, and other conditions associated with sellar mass effect lead to global failure of pituitary function and hypopituitarism. In these situiations, prolactin is commonly the last pituitary hormone affected, after growth hormone and gonadotropins are lost and thyroid-stimulating hormone and adrenocorticotopic hormone secretion is impaired. Prolactin deficiency accompanies several congenital syndromes due to mutations in PROP1 and Pit1/ POU1F and in X-linked IGSF1 deficiency syndrome, and several aqcuired conditions including Sheehan syndrome, IgG4-related hypophysitis, and immune checkpoint-inhibitor-induced hypophysitis. In women, prolactin deficiency prevents lactation following childbirth among other symptoms associated with hypopituitarism. Human prolactin is not available commercially as replacement therapy. However, recombinant human prolactin administered daily to women with hypoprolactinemia and alactogenesis was found to lead to the production of significant milk volume sufficient for lactation.

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.

Both local and external cranial radiotherapy (RT) can induce neurotoxicity and vascular damage of the hypothalamic-pituitary area, which can promote neuroendocrine alterations. While anterior pituitary insufficiency after RT has been extensively characterized, data on the effect of RT on prolactin (PRL) secretion are limited and heterogeneous, with different patterns of PRL behavior described in the literature. A progressive decline in PRL levels, reflecting a time-dependent, slowly evolving radiation-induced damage to the pituitary lactotroph cells has been reported. To date, the association between hypopituitarism and hypoprolactinemia in patients undergoing RT has not yet been fully investigated. The few available data suggest that lower PRL levels can predict an extent damage of the pituitary tissue and a higher degree of hypothalamic dysfunction. However, most studies on the effect of RT on pituitary function do not properly assess PRL secretion, as PRL deficiency is usually detected as part of hypopituitarism and not systematically investigated as an isolated disorder, which may lead to an underestimation of hypoprolactinemia after RT. In addition, the often-inadequate follow-up over a long period of time may contribute to the non-recognition of PRL deficiency after RT. Considering that hypoprolactinemia is associated with various metabolic complications, there is a need to define appropriate diagnostic and management criteria. Therefore, hypoprolactinemia should enter in the clinical investigation of patients at risk for hypopituitarism, mainly in those patients who underwent RT.

Traumatic brain injury (TBI) is a well-known etiologic factor for pituitary dysfunctions, with a prevalence of 15% during long-term follow-up. The most common hormonal disruption is growth hormone deficiency, followed by central adrenal insufficiency, central hypogonadism, and central hypothyroidism in varying order across studies. The prevalence of serum prolactin disturbances ranged widely from 0 to 85%. Prolactin release is mainly regulated by hypothalamic dopamine inhibition, and mediators such as TRH, serotonin, cytokines, and neurotransmitters have modulatory effects. Many factors, such as hypothalamic and/or pituitary gland injuries, as well as fluctuations in dopaminergic activity and other mediators and stress response, may cause derangements in serum prolactin levels after TBI. Although it is challenging to investigate the direct effects of TBI on serum prolactin levels due to many confounders, basal prolactin measurements and stimulation tests provide insight into the functionality of the hypothalamus and pituitary gland after TBI. Moreover, during the acute phase of TBI, prolactin levels appear to correlate with TBI severity. In contrast, in the chronic phase, hypoprolactinemia may function as an indirect indicator of pituitary dysfunction and reduced pituitary volume. Further investigations are needed to elucidate the pathophysiologic mechanisms underlying the prolactin trend following TBI, its significance, and its associations with other pituitary hormone dysfunctions. In this article, we re-evaluated our patients' TBI data regarding prolactin levels during prospective long-term follow-up, and reviewed the literature regarding the prevalence, pathophysiology, and clinical implications of serum prolactin disturbances during acute and chronic phases following TBI.

Prolactin is a polypeptide hormone composed of 199 amino acids, synthesized by lactotroph cells. Its primary effects are on the mammary gland and gonadal axes, but it also influences different organs and systems, particularly metabolic functions. Current literature has mainly focused on the diagnosis, monitoring, and treatment of hyperprolactinemia. Due to the lack of a well-established effective treatment for hypoprolactinemia, it is not clinically emphasized. Therefore, data on its diagnosis is limited. Hypoprolactinemia has been associated with metabolic dysfunctions such as type 2 diabetes mellitus, fatty liver, dyslipidemia, fertility problems, sexual dysfunction, and increased cardiovascular disease. While often seen as a part of combined hormone deficiencies due to pituitary damage, isolated prolactin deficiency is rare. Hypoprolactinemia can serve as a marker for extensive pituitary gland damage and dysfunction.Low or undetectable serum prolactin levels and the absence of a sufficient prolactin peak in the thyrotropin-releasing hormone (TRH) stimulation test are considered diagnostic for hypoprolactinemia. Gender appears to influence both basal prolactin levels and TRH stimulation test responses. Basal prolactin levels of, at least, 5 ng/mL for males and 7 ng/mL for females can be used as cut-off levels for normal prolactin reserve. Minimum peak prolactin responses of 18 ng/mL for males and 41 ng/mL for females to TRH stimulation can exclude hypoprolactinemia. However, larger population studies across different age groups and sexes are needed to better define normal basal prolactin levels and prolactin responses to the TRH stimulation test.

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.

This special issue of Reviews in Endocrine and Metabolic Disorders is dedicated to hypoprolactinemia. Prolactin is known for its actions on the mammary gland including development, preparation for postpartum lactation, as well as synthesis and maintenance of milk secretion. However, prolactin has many other physiological effects on reproduction, embryonic and fetal development, homeostasis, neuroprotection, behavior, and immunoregulation. In clinical practice, physiopathology and clinical consequences of increased prolactin secretion are generally well understood, and medical treatment to decrease prolactin levels is available and effective in most cases. Unlike prolactin excess, hypoprolactinemia has been a neglected endocrine disorder and nospecific replacement therapy is commercially available. Prolactin is the only anterior pituitary hormone not addressed by clinical hypopituitarism guidelines. In recent years, human studies have revealed that hypoprolactinemia is associated with metabolic, sexual and neuropsychologic alterations. Therefore, this special issue of Reviews in Endocrine and Metabolic Disorders is aimed to enhance our incomplete understanding of hypoprolactinemia. A total of 17 articles were authored by respected scientists and clinicians from a variety of disciplines including adult and pediatric endocrinology, pathology, gynecology, reproductive medicine, oncology, and neurosurgery.