Prolactin Recovery Research Articles

Screening for Prolactin Isoforms in the Follicular Fluid of Patients Undergoing in vitro Fertilization

The purpose of this prospective and non-randomized study was to identify prolactin (PRL) isoforms in the follicular fluid (FF) of patients undergoing in vitro fertilization (IVF). The FF from 19 patients was obtained during oocyte retrieval at the University Hospital, Ribeirão Preto Medical School. The molecular weight of FF PRL was determined by column chromatography on Sephacryl S-200 HR combined with an immunometric assay. The only PRL isoform detected in FF exhibited a molecular weight of 20.5 kD. The molecular weights of FF PRL and small PRL are essentially identical. The 20.5-kD PRL accounted for 93.1 ± 9.1% (mean ± SD) of the recovered PRL after gel chromatography. Total PRL recovery was 74.2 ± 19%. Thus, the only PRL detected in the FF was the small PRL, the most potent one.

Circulating anti-prolactin auto-antibodies must be considered in the differential diagnosis of hyperprolactinaemia in adolescents.

In four adolescents (two girls and two boys), who were investigated for galactorrhoea or short stature, we found moderately elevated serum prolactin (PRL) levels, but without a decreased gonadotropin and sex hormone production. Serum PRL levels were not responding to the intravenous injection of thyrotropin releasing hormone. Magnetic resonance imaging of the hypothalamic-pituitary region revealed no abnormality. Initial diagnoses were idiopathic and drug-induced hyperprolactinaemia. The presence of anti-prolactin auto-antibodies was suspected because of low recovery of PRL after precipitation with polyethylene glycol and confirmed by immunoprecipitation with anti-human IgG-agarose. anti-prolactin auto-antibodies causing high prolactin values in some immunoassays can cause hyperprolactinaemia in adolescents without other signs of hormonal disturbances or auto-immune disease.

Free prolactin determinations in hyperprolactinemic men with suspicion of macroprolactinemia

Background: The Elecsys® prolactin (PRL) assay reacts more strongly with macroprolactin than the Centaur® PRL assay. We evaluated Elecsys direct and free PRL measurements vs. Centaur direct PRL measurements, in sera with and without macroprolactin. Methods: PRL was measured using Elecsys and Centaur direct assays and the Elecsys assay in the supernatant obtained after PEG precipitation (free PRL) in 34 sera from 34 hyperprolactinemic male subjects (Elecsys direct PRL>434 mIU/l) classified, according to the PRL recovery after PEG precipitation, as: negative, i.e. without predominant macroprolactin (recovery %>50, n=12), positive (recovery %<40, n=18) or indeterminate ( n=4). Results: The positive bias between Elecsys direct and Centaur PRL results was clearly influenced by the presence of macroprolactin and the mean bias between Elecsys free and Centaur prolactin values was near zero in the negative and positive groups. Among 14 patients from the positive group presenting clinical conditions possibly ascribable to hyperprolactinemia, Elecsys free and Centaur PRL levels were normal in seven and increased in five. In the negative and positive groups considered together, Elecsys free PRL agreed well with Centaur prolactin (28/30). The poor concordance observed for the indeterminate samples underlined the heterogeneity of macroprolactin. Conclusion: Elecsys free PRL determination can be used to reduce the marked influence of macroprolactin in this assay.

An Unusual Form of Big, Big (Macro) Prolactin in a Pregnant Patient

It is well recognized that circulating prolactin may exist in several forms, including little (monomeric), big, and big, big (macroprolactin) prolactin with molecular masses of 23, 50, and 150–170 kDa, respectively (1). We report the case of a 30-year-old woman who initially attended her primary care physician because of the onset of painful irregular periods. Her cycle usually was regular, but she had had an 8-week interval of amenorrhea, followed by a particularly painful bleed for which she sought medical advice. Before this, and subsequently, her menstruation had been completely regular with a 28-day cycle. She had no other problems. The patient’s initial serum prolactin was recorded as 15 800 mIU/L (∼530 μg/L) in a Bayer Immuno 1TM assay (Bayer Corporation). Other investigations at the time were entirely normal. When the subject was monitored 2 months later, she was symptomless and menstruating regularly; her serum prolactin, using the same assay as before, was 8440 mIU/L (∼270 μg/L). Pituitary imaging by magnetic resonance was normal. She had, of choice, never been pregnant. Because of the patient’s lack of symptoms, normal pituitary imaging, and regular cycles, further analytical investigations were carried out on a sample of her serum. After polyethylene glycol (PEG) precipitation, the recovery of prolactin was low, indicating the presence of macroprolactin (2), and 15% of her total prolactin was estimated to be monomeric prolactin. …

Macroprolactinaemia: validation and application of the polyethylene glycol precipitation test and clinical characterization of the condition.

The clinical characteristics and natural history of macroprolactinaemia are yet to be fully established and there is currently no widely accepted simple in vitro test for routine identification of the condition. This study was designed to further validate the polyethylene glycol (PEG) precipitation test with assessment of percentage prolactin recovery (%R), for the detection of macroprolactinaemia and clinically characterize cases identified using the test. Analytical validation and application of the PEG precipitation test for diagnosis of macroprolactinaemia and a retrospective case-notes review of some of the patients identified with the condition. Sera from 188 patients with elevated serum prolactin (PRL) concentrations were screened for macroprolactinaemia. Seventeen of the patients who were under follow-up at the local teaching hospital and were identified to have macroprolactinaemia were systematically characterized clinically. Prolactin was measured in sera, fractions from gel filtration chromatography and supernatant obtained after PEG precipitation, by the DELFIA fluoroimmunoassay. CLINICAL ENDPOINTS: Initial serum PRL and symptoms and their response to dopamine agonist therapy; imaging of the pituitary gland; serum PRL and symptoms after cessation of dopamine agonist therapy; course of serum PRL and symptoms without dopamine agonist therapy. The within-batch coefficient of variation (CV) of the PEG precipitation test ranged between 2.8 and 7.3% while the between-batch CV ranged between 3.4 and 9.7%. Intra-individual variability up to five months was 9.9%. A prolactin recovery </= 40% was indicative of macroprolactinaemia, while the condition was unlikely to be present at values > 50%. The prevalence of macroprolactinaemia was 15% without sex difference. Clinical characterization of 17 patients showed modest initial serum PRL concentrations and there was imaging evidence of a coexisting pituitary adenoma in three of them. Dopamine agonist therapy resulted in substantial falls in serum PRL and this was associated with improvement or resolution of symptoms in some patients. Stoppage of dopamine agonist resulted in rebound hyperprolactinaemia in all cases. Spontaneous improvement in symptoms occurred in three patients but hyperprolactinaemia persisted in all those who were not on treatment. The PEG precipitation test with assessment of 'free' prolactin has been shown to be reproducible and sensitive for the detection of macroprolactinaemia. Many of the patients who had macroprolactinaemia presented with at least one symptom of the hyperprolactinaemic syndrome. Dopaminergic therapy may influence the course of both serum PRL and symptoms in some of these patients.

Macroprolactinaemia: contribution to hyperprolactinaemia in a district general hospital and evaluation of a screening test based on precipitation with polyethylene glycol.

For a period of 12 months all samples submitted for serum prolactin (PRL) assay and with PRL > 700 mU/L were examined by gel filtration chromatography. In 17 (25%) of 69 samples we found macroprolactin. The Delfia and Immuno 1 immunoassay systems gave similar PRL results with samples containing macroprolactin whereas the ACS 180 system gave lower results. With the Delfia and Immuno 1 systems samples containing substantial quantities of macroprolactin showed low recovery of PRL after precipitation with polyethylene glycol 6000 (PEG 6000) and this technique can be used as a screening test for macroprolactinaemia. We conclude that macroprolactinaemia is a common phenomenon and, in assays which detect this species, is a common cause of hyperprolactinaemia. Macroprolactinaemia may contribute to the difficulty in establishing an upper limit of the reference range for serum PRL. In our experience, patients with macroprolactinaemia do not exhibit features of the hyperprolactinaemia syndrome and it is important to recognize macroprolactin as the cause of hyperprolactinaemia to avoid unnecessary investigation and treatment.

Preferential interaction of [35S]cysteamine with pituitary secretory granule storage forms of prolactin.

Cysteamine (CySH) inhibits the immunodetectability and bioactivity of prolactin (PRL), and we have proposed that it may act by impeding the conversion from secretory granule hormone storage forms to releasable and assayable hormone. This process appears to be dependent upon thiol:disulfide interchange reactions, which can be inhibited by the aminothiol. The present studies utilized [35S]CySH to determine whether preferential interactions could be demonstrated between CySH and bovine pituitary storage hormone forms as opposed to monomeric PRL. [35S]CySH was incubated with purified intact secretory granules, with granule 'core' preparations enriched in oligomeric forms by prior hypotonic exposure, with chromatographically isolated oligomers, and with monomeric PRL. Binding to granules was saturable and pH-dependent with greatest binding observed at pH 7.5-8.0. Binding to monomer was much less than binding to all other fractions, being 20% or less than that to any other form. HPLC studies of granules treated with [35S]CySH indicated that exposure to CySH was associated with a predominance of very high molecular weight oligomers. These forms were entrapped on the gel permeation columns, resulting in decreased protein and PRL recovery; as little as 6.6% of the PRL was eluted after 60 min of CySH exposure. CySH not only bound to storage forms of PRL but also to secretory granule membranes; whether the bioeffect is mediated through membrane modifications is unknown. Despite its relative ineffectiveness at altering growth hormone immunoactivity or secretion, CySH nonetheless also bound to growth hormone.(ABSTRACT TRUNCATED AT 250 WORDS)

Resumption of prolactin secretion after dopaminergic inhibition: differential effects of dopamine and its agonists.

The recovery of prolactin (PRL) secretion following dopaminergic inhibition was studied in vitro using pituitary monolayer cultures. PRL secretion over 4 h was inhibited comparably by 10(-6) M dopamine (DA), 10(-7) M apomorphine (APO), and 10(-10) M bromocriptine (45%, 42%, 51%, respectively) with reciprocal increases in intracellular hormone content. After drug removal, the PRL secretion rate in the cultures that had been treated with DA was 208% of the control cultures by the 2nd h but returned to control values by 4 h, whereas the secretion rate after APO was 131-142% of control throughout the 4-h recovery period. In contrast, PRL secretion remained significantly less than control 20 h after the removal of bromocriptine. Although haloperidol (10(-7) M) prevented the inhibitory action of bromocriptine when added simultaneously, the addition of haloperidol did not restore PRL secretion when added in the posttreatment period. Thus, DA and APO inhibition of PRL release is readily reversible and is followed by early PRL hypersecretion. However, bromocriptine's effects are sustained and once started are not reversed by DA antagonists.

Recovery of prolactin from acetone-dried human pituitary glands.

An improved method is described for the purification of prolactin from the same batch of acetone-dried pituitary glands which is used for the isolation of other anterior pituitary hormones. The residue obtained after the extraction of the glycoprotein fraction from the pituitary acetone powder was extracted for growth hormone. The supernatant after the precipitation of growth hormone at 50% ethanol concentration was adjusted to 85% in ethanol. To the supernatant obtained from that step an equal volume of acetone was added to precipitate the 'PRL fraction.' This fraction was further purified by gel filtration on Sephadex G-100, ion-exchange chromatography on DEAE-cellulose and isoelectric focussing. A yield of 23 mg prolactin, 37 U/mg, was obtained per 1000 g pituitary acetone powder.