Technology insight: measuring prolactin in clinical samples

Quasi-spherical silver nanoparticles for human prolactin detection by surface-enhanced Raman spectroscopy

Prolactin is a polypeptide hormone made of 199 amino acids; 50% of the amino acid chain forms helices, and the rest forms loops. This hormone is typically related to initiating and maintaining lactation, although it is also elevated in various pathological conditions. Serum prolactin levels of 2 to 18 ng ml-1 in men, up to 30 ng ml-1 in women, and 10 to 210 ng ml-1 in pregnant women are considered normal. Immunoassay techniques used for detection are susceptible to error in different clinical conditions. Surface-enhanced Raman spectroscopy (SERS) is a technique that allows for obtaining the protein spectrum in a simple, fast, and reproducible manner. Nonetheless, proper characterization of human prolactin's Raman/SERS spectrum at different concentrations has so far not been deeply discussed. This study aims to characterize the Raman spectrum of human prolactin at physiological concentrations using silver nanoparticles (AgNPs) as the SERS substrate. The Raman spectrum of prolactin at 20 ng ul-1 was acquired. Quasi-spherical AgNPs were obtained using chemical synthesis. For SERS characterization, decreasing dilutions of the protein were made by adding deionized water and then a 1 : 1 volume of the AgNPs colloid. For each mixture, the Raman spectrum was determined. The spectrum of prolactin by SERS was obtained with a concentration of up to 0.1 ng ml-1. It showed characteristic bands corresponding to the side chains of aromatic amino acids in the protein's primary structure and the alpha helices of the secondary structure of prolactin. In conclusion, using quasi-spherical silver nanoparticles as the SERS substrate, the Raman spectrum of human prolactin at physiological concentration was determined.

A new method for broadening the detection range of immunoassay and its application in β-hCG quantitative detection

Early pregnancy prediction requires very high β-hCG detection sensitivity, while embryonic development monitoring and trophoblastic disease detection require a wider detection range. In this study, based on light-initiated chemiluminescence assay (LICA), one high-affinity mAb and one low-affinity mAb were selected and coated on chemibeads with a larger coating area in different ratios to immobilize the antibodies. The two immobilized mAbs were mixed with different concentrations to detect β-hCG. When the high-affinity mAb-coated chemibeads and low-affinity mAb-coated chemibeads were used at working concentrations of 0.100 mg mL^-1 and 0.014 mg mL^-1, respectively, the sensitivity and detection range were maximized. The assay was precise for measuring β-hCG with repeatability and intermediate precision of <5% CV. The assay has a high sensitivity with a limit of quantification (LoQ) of 0.49 IU L^-1, which is lower than that of most β-hCG detection kits. Over the range of 1 IU L^-1 to 16 000 IU L^-1, the assay had a proper linearity (r = 0.9995). No false negative results due to the hook effect were observed at β-hCG concentrations up to 225 000 IU L^-1. The assay showed a good correlation with the Abbott assay (r = 0.9910). LICA combined with immobilized mAbs with different affinities ensures the sensitivity of β-hCG detection and broadens the detection range.

Persistent Idiopathic Prolactin Elevation Merits Macroprolactin Estimation: A Case Report and Review of Literature

The prevalence of hyperprolactinemia ranges from about 0.4% in an unselected adult population to as high as 9%–17% in women with reproductive disorders. It may cause infertility in about 11% of the oligospermic males. Rarely, the cause of persistently elevated prolactin remains obscure even after thorough work up. Macroprolactinemia is biologically inactive, high-molecular-weight form of prolactin resulting from its binding to immunoglobulin G, causing a decrease in its clearance. We report the case of a 35-year-old female, detected to have hyperprolactinemia on multiple tests, during routine work up for primary infertility. Secondary causes for the same were ruled out. A magnetic resonance imaging (MRI) of the brain excluded a prolactinoma. This prompted an estimation of prolactin levels after polyethylene glycol precipitation which showed a decrease to 5.58 ng/mL, with <40% recovery, confirming the presence of macroprolactin. Thus, persistently elevated prolactin levels in the background of negative neurological imaging necessitate the estimation of macroprolactin.

Prolactin and Other Pituitary Disorders in Kidney Disease

Prolactin levels are increased in chronic kidney disease (CKD) as a result of reduced clearance and increased secretion. Hyperprolactinemia manifests as galactorrhea and hypogonadism. Treatment of hyperprolactinemia should focus on improving bothersome galactorrhea or hypogonadism by using dopamine agonists and/or replacement of sex hormone(s). Changes in the hypothalamic-pituitary-adrenal axis in CKD are characterized by increases in adrenocorticotropic hormone (ACTH) and cortisol levels, largely preserved circadian rhythms of ACTH and cortisol, and a normal response of cortisol to ACTH, metyrapone, and insulin-induced hypoglycemia. However, the hypothalamic-pituitary-adrenal axis is less inhibited by 1 mg dexamethasone but retains normal suppression by higher-dose dexamethasone. Diagnosis of adrenal insufficiency in CKD patients, as in normal subjects, usually is made by finding a subnormal cortisol response to ACTH. The mainstay of treatment of adrenal insufficiency is to replace glucocorticoid hormone. Cushing's disease in CKD is difficult to diagnose and relies on the dexamethasone suppression test and the midnight salivary cortisol test because the 24-hour urine free cortisol test is not useful because it is increased already in CKD. Treatment of Cushing's disease involves surgery, complemented by radiation and/or medical therapy if necessary. Growth hormone levels are increased and insulin-like growth factor 1 levels are normal in patients with CKD. In a normal patient with CKD, as in one with acromegaly, there can be a paradoxic increase in growth hormone after an oral glucose load. Therefore, diagnosis of acromegaly in renal insufficiency is challenging. The treatment of choice for acromegaly is surgery, although data for medical treatment for acromegaly in CKD are rare. In patients with renal impairment, arginine vasopressin levels are increased as a result of decreased clearance, and there also is impairment of arginine vasopressin signaling in renal tubules. Diabetes insipidus can be masked in advanced kidney disease until kidney transplantation. Diagnosis of the syndrome of inappropriate antidiuretic hormone is similar in mild or moderate kidney disease as in normal subjects, but is challenging in patients with advanced kidney disease owing to the impairment in urine dilution.

Pituitary Tumors Centers of Excellence

Pituitary tumors are common and require complex and sophisticated procedures for both diagnosis and therapy. To maintain the highest standards of quality, it is proposed to manage patients in pituitary tumors centers of excellence (PTCOEs) with patient-centric organizations, with expert clinical endocrinologists and neurosurgeons forming the core. That core needs to be supported by experts from different disciplines such as neuroradiology, neuropathology, radiation oncology, neuro-ophthalmology, otorhinolaryngology, and trained nursing. To provide high-level medical care to patients with pituitary tumors, PTCOEs further pituitary science through research publication, presentation of results at meetings, and performing clinical trials.

The epidemiology, diagnosis and treatment of Prolactinomas: The old and the new

Prevalence and incidence of prolactinomas are approximately 50 per 100,000 and 3-5 new cases/100,000/year. The pathophysiological mechanism of hyperprolactinemia-induced gonadotropic failure involves kisspeptin neurons. Prolactinomas in males are larger, more invasive and less sensitive to dopamine agonists (DAs). Macroprolactin, responsible for pseudohyperprolactinemia is a frequent pitfall of prolactin assay. DAs still represent the primary therapy for most prolactinomas, but neurosurgery has regained interest, due to progress in surgical techniques and a high success rate in microprolactinoma, as well as to some underestimated side effects of long-term DA treatment, such as impulse control disorders or impaired quality of life. Recent data show that the suspected effects of DAs on cardiac valves in patients with prolactinomas are reassuring. Finally, temozolomide has emerged as a valuable treatment for rare cases of aggressive and malignant prolactinomas that do not respond to all other conventional treatments.

Clinical manifestations, evaluation and management of hyperprolactinemia in adolescent and young girls: a brief review

Hyperprolactinemia (HPrl) is considered as a rare endocrinopathy in childhood. In children and adolescent girls, there are three major categories of HPrl causes; physiological, pathological and iatrogenic. Through hypogonadotropic hypogonadism, prolactin hypersecretion and production leads to the typical functional syndrome which is observed in female children and adolescents; delayed puberty, primary or secondary amenorrhea and/or galactorrhea. Regarding prolactinomas, clinical signs manifest with mass compression of the optic chiasm and anterior pituitary gland or prolactin hypersecretion. Targeted identification of HPrl is of significant importance for proper management and follow-up. The aim of this review is to focus on the evaluation of HPrl in adolescent and young girls. In addition, we aimed to summarize the current knowledge regarding the proper management of such cases. (www.actabiomedica.it)

Frequency of Macroprolactinemia in Hyperprolactinemic Women Presenting with Menstrual Irregularities, Galactorrhea, and/or Infertility: Etiology and Clinical Manifestations

Aim. To determine the frequency of macroprolactinemia, its etiology, and the clinical manifestations in patients with hyperprolactinemia presenting with menstrual irregularities, galactorrhea, and/or infertility who were attended by the gynecology-endocrinology service. Methods. In a cross-sectional study, 326 hyperprolactinemic women were tested for serum prolactin (PRL) concentrations before and after chromatographic separation (gel filtration and affinity with protein G) and extraction of free PRL with polyethylene glycol (PEG). Results. Sera from 57 patients (17.5%) were found to have macroprolactinemia. The presence of macroprolactinemia was attributable to anti-PRL autoantibodies in 54 (94.7%) patients. The median serum PRL levels were similar in patients with or without macroprolactinemia (42.0 versus 38.1 ng/mL). In contrast, patients with macroprolactinemia had lower serum-free PRL levels (median 9.2 versus 31.7 ng/mL, P < 0.001). Patients without macroprolactinemia had a higher frequency of galactorrhea and abnormal pituitary imagine findings (P < 0.002). Conclusions. We can conclude that macroprolactinemia should be considered as a benign variant, and it must be ruled out in women presenting with menstrual irregularities, galactorrhea, and/or infertility in order to investigate other causes different than hyperprolactinemia. Serum PRL precipitated with PEG is a convenient and simple procedure to screen for the presence of macroprolactinemia.

The importance of measuring macroprolactin in the differential diagnosis of hyperprolactinemic patients

This study investigated the differences in clinical and laboratory features as well as treatment response in 70 outpatients with macroprolactinemia and monomeric hyperprolactinemia treated with dopamine agonists. After precipitation of the patients' serum samples with poly-ethylene-glycol (PEG), serum prolactin (PRL) levels were measured. We also measured serum levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol for women and testosterone for men. Clinical symptoms and signs were recorded. All patients received brain magnetic resonance imaging (MRI). After excluding patients with macroadenoma, 66 patients were treated with the dopamine agonist cabergoline. After 1 year, the clinical responses to cabergoline were recorded and PRL levels measured. Of the initial 70 patients with hyperprolactinemia, 15 patients (21.4%) were found to have macroprolactinemia, while the rest had monomeric hyperprolactinemia. The two groups did not differ with regard to galactorrhea, menstrual disturbances or impotence. There were no significant group differences in serum LH, FSH, estradiol or testosterone levels. Patients with macroprolactinemia, however, had a significantly lower infertility rate than those with true hyperprolactinemia (6.7% vs. 32.7%, p=0.005). A greater percentage of macroprolactinemic patients had normal MRI pituitary images than those with hyperprolactinemia (73.3% vs. 34.5%, p=0.029). Compared to those with true hyperprolactinemia, patients with macroprolactinemia were found to have no significant changes in clinical features and PRL levels after 1 year of cabergoline therapy (after PEG precipitation, pre- and post-PRL levels: 59.3 ± 100.2 to 13.8 ± 9.5 ng/mL vs. 6.1 ± 5.3 to 5.1 ± 4.3 ng/mL, p=0.002). In conclusion, while macroprolactinemia is a common cause of hyperprolactinemia, many clinical and laboratory features cannot be used reliably to differentiate macroprolactinemia from true hyperprolactinemia. Routine screening for all hyperprolactinemic sera with PEG might prevent the unnecessary use of image studies and medical treatments for people with hyperprolactinemia.

Prevalence of endocrine diseases in morbidly obese patients scheduled for bariatric surgery: beyond diabetes

BACKGROUND

Bariatric surgery allows stable body weight reduction in morbidly obese patients. In presurgical evaluation, obesity-related co-morbidities must be considered, and a multidisciplinary approach is recommended. Precise guidelines concerning the endocrinological evaluation to be performed before surgery are not available. The aim of this study was to evaluate the prevalence of common endocrine diseases in a series of obese patients scheduled for bariatric surgery.

METHODS

We examined 783 consecutive obese subjects (174 males and 609 females) aged 18-65 years, who turned to the obesity centre of our department from January 2004 to December 2007 for evaluation before bariatric surgery. Thyroid, parathyroid, adrenal and pituitary function was evaluated by measurement of serum hormones. Specific imaging or supplementary diagnostic tests were performed when indicated.

RESULTS

The overall prevalence of endocrine diseases, not including type 2 diabetes mellitus, was 47.4%. The prevalence of primary hypothyroidism was 18.1%; pituitary disease was observed in 1.9%, Cushing syndrome in 0.8%, while other diseases were found in less than 1% of subjects. Remarkably, the prevalence of newly diagnosed endocrine disorders was 16.3%.

CONCLUSIONS

A careful endocrinological evaluation of obese subjects scheduled for bariatric surgery may reveal undiagnosed dysfunctions that require specific therapy and/or contraindicate the surgical treatment in a substantial proportion of patients. These results may help to define the extent of the endocrinological screening to be performed in obese patients undergoing bariatric surgery.

Comparison of multiple methods for identification of hyperprolactinemia in the presence of macroprolactin

BACKGROUND

Macroprolactin is a large, heterogeneous form of prolactin with limited bioavailability. Detection of macroprolactin by different immunoassays varies widely. The objectives of this study were to determine the immunoreactivity of macroprolactin by the Ortho Clinical Diagnostics Vitros((R)) ECi prolactin immunoassay, establish the most effective method for interpreting the prolactin concentration after PEG-precipitation, and correlate the clinical features of hyperprolactinemia with the presence of macroprolactin.

METHODS

PEG-precipitation was performed on 120 hyperprolactinemic specimens. Of these, 31 specimens with a recovery<80% were fractionated by GFC. Four different approaches for identifying true hyperprolactinemia were investigated. Clinical symptoms of hyperprolactinemia were determined by chart review.

RESULTS

Macroprolactin was detected by the Vitros ECi prolactin immunoassay. Use of a PEG modified prolactin reference interval was effective for identifying hyperprolactinemia in the presence of macroprolactin. There was no difference in the prevalence of abnormal menses, galactorrhea, or abnormal MRI between those with and without macroprolactin (p>0.05). Accounting for macroprolactin in patients with hyperprolactinemia reduced the number of idiopathic cases.

CONCLUSIONS

The Vitros ECi prolactin immunoassay detects macroprolactin. PEG-precipitation is an acceptable surrogate to detect hyperprolactinemia in the presence of macroprolactin when using a prolactin reference interval derived from PEG precipitated reference sera. Although testing for macroprolactin should not substitute for standard evaluation of hyperprolactinemia, identification of macroprolactin may clarify a diagnosis and direct appropriate therapy.

Should macroprolactin be measured in all hyperprolactinaemic sera?

Macroprolactin is a nonbioactive prolactin isoform usually composed of a monomer of prolactin and a IgG molecule which has a prolonged clearance rate similar to that of the immunoglobulins. Macroprolactinaemia, hyperprolactinaemia entirely accounted for by the presence of macroprolactin, is estimated to account for approximately 10% of all hyperprolactinaemia coming to clinical attention in the United Kingdom and the United States. Failure to recognize that macroprolactinaemia can explain hyperprolactinaemia, leads to unnecessary investigation, incorrect diagnosis and inappropriate treatment. Screening of hyperprolactinaemic sera for the presence of misleading concentrations of macroprolactin is readily performed in biochemistry laboratories although the procedures have not been automated. The most widely employed method is to treat the hyperprolactinaemic sera with polyethylene glycol which precipitates out high-molecular weight constituents including immunoglobulins. Re-assay of the sera for prolactin will then identify those sera which yield values within the relevant normal range indicative of macroprolactinaemia and not true hyperprolactinaemia. The case for the routine screening of all hyperprolactinaemic sera for macroprolactin is compelling. The consequences of failure to recognize macroprolactinaemia are significant, the problem is frequently encountered, the means of addressing it are immediately available and it is cost effective.

Treatment with low doses of cabergoline is not associated with increased prevalence of cardiac valve regurgitation in patients with hyperprolactinaemia

INTRODUCTION AND AIM

Dopamine agonists have been reported to increase the risk of cardiac valve regurgitation in patients with Parkinson's disease. However, it is unknown whether these drugs might be harmful for patients with hyperprolactinaemia (HyperPRL). The aim of the study was to evaluate whether HyperPRL patients treated with dopamine agonists had a higher prevalence of cardiac valves regurgitation than that of general population.

METHODS AND PATIENTS

One hundred consecutive patients (79 women, 21 men, mean age 41 +/- 13 years) with HyperPRL during treatment with cabergoline were enrolled in an observational case-control study and compared with 100 matched normal subjects (controls). Valve regurgitation was assessed by echocardiography according to the American Society of Echocardiography recommendations.

RESULTS

Seven HyperPRL patients (7%) and six controls (6%) had moderate (grade 3) regurgitation in any valve (p = 0.980). All were asymptomatic and had no signs of cardiac disease. Mean duration of cabergoline treatment was 67 +/- 39 months (range: 3-199 months). Mean cumulative dose of cabergoline was 279 +/- 301 mg (range: 15-1327 mg). Moderate valve regurgitation was not associated with the duration of treatment (p = 0.359), with cumulative dose of cabergoline (p = 0.173), with age (p = 0.281), with previous treatment with bromocriptine (p = 0.673) or previous adenomectomy (p = 0.497) in patients with HyperPRL.

DISCUSSION

In conclusion, treatment with cabergoline was not associated with increased prevalence of cardiac valves regurgitation in patients with HyperPRL. Mean cumulative dose of cabergoline was lower in patients with HyperPRL than that reported to be deleterious for patients with Parkinson's disease: hence, longer follow-up is necessary, particularly in patients receiving weekly doses > 3 mg.

Hyperprolactinemia and prolactinomas

Any process interfering with dopamine synthesis, its transport to the pituitary gland, or its action at the level of lactotroph dopamine receptors can cause hyperprolactinemia. As described in this article, considering the complexity of prolactin regulation, many factors could cause hyperprolactinemia, and hyperprolactinemia can have clinical effects not only on the reproductive axis. Once any drug effects are excluded, prolactinomas are the most common cause of hyperprolactinemia. The most frequent symptom is hypogonadism in both genders. Medical and surgical therapies generally have excellent results, and most prolactinomas are well controlled or even cured in some cases.