Is prolactin secreted ectopically?

Armadilhas no diagnóstico da hiperprolactinemia

Na abordagem diagnóstica da hiperprolactinemia, três armadilhas ou problemas potenciais merecem uma atenção especial: os incidentalomas hipofisários (presentes em 10% da população adulta à ressonância magnética), o efeito gancho e a macroprolactinemia. O efeito gancho se caracteriza pela presença de níveis falsamente baixos de prolactina (PRL), quando se empregam imunoensaios de dois sítios em pacientes com grandes prolactinomas e hiperprolactinemia muito acentuada. O efeito gancho pode ser identificado através de uma nova dosagem da PRL após diluição do soro a 1:100, quando se observará um aumento dramático do valor da PRL. Ele deve ser excluído em qualquer paciente com um macroadenoma e níveis séricos de PRL <200ng/mL. A macroprolactinemia responde por cerca de 10% dos casos de hiperprolactinemia. Resulta de um excesso de PRL polimérica (macroprolactina ou big big prolactin), cuja biodisponibilidade é diminuída. Assim, a maioria dos pacientes com macroprolactinemia não apresenta os sintomas clássicos da hiperprolactinemia e habitualmente não requerem tratamento.

Medical management of prolactin-secreting pituitary adenomas

Prolactinomas are a common cause of reproductive/sexual dysfunction. Once other causes of hyperprolactinemia have been excluded with a careful history and physical examination, routine chemistries, a pregnancy test and a TSH, imaging with MRI or CT will delineate the size and extent of the tumor. Medical therapy is the initial treatment of choice. When infertility is the primary indication for treatment, bromocriptine use has an extensive safety experience and is preferred. However, for other indications, cabergoline appears to be more efficacious and better tolerated. Transsphenoidal surgery remains an option, especially for patients with microadenomas, when medical therapy is ineffective.

Disorders of prolactin secretion

Prolactinomas are a common cause of reproductive/sexual dysfunction. Once other causes of hyperprolactinemia have been excluded with a careful history and physical examination, routine chemistries, and an assay for TSH, MR imaging, or CT will delineate the size and extent of the tumor. Medical therapy is the initial treatment of choice. When infertility is the primary indication for treatment, bromocriptine use has an extensive safety record and is preferred. For other indications, cabergoline seems to be more efficacious and better tolerated. Transsphenoidal surgery remains an option, especially for patients with microadenomas, when medical therapy is ineffective.

Ectopic production of prolactin by colorectal adenocarcinoma

PURPOSE

This study assessed the role of prolactin in patients with Dukes B and C colorectal carcinoma.

METHODS

Circulating prolactin and carcinoembryonic antigen were assayed using immunoradiometric assay and radioimmunoassay kits, respectively, in preoperative blood (n = 98) and tumor-draining venous blood (n = 34) samples of colorectal carcinoma patients. Immunohistochemical localization of prolactin (n = 98), carcinoembryonic antigen (n = 98), and prolactin receptors (n = 56) was performed. The expression of prolactin messenger ribonucleic acid (n = 50) and prolactin receptor messenger ribonucleic acid (n = 50) was studied by reverse transcriptase polymerase chain reaction. Further, prolactin amplimer was sequenced.

RESULTS

Preoperative prolactin and carcinoembryonic antigen levels were significantly higher in patients with colorectal carcinoma than in controls (prolactin, P = 0.001; carcinoembryonic antigen, P = 0.0001). Univariate survival analysis showed that Dukes stage, histologic grade, and circulating prolactin were significant prognostic factors for determining overall survival (Dukes stage, P = 0.00001; histologic grade, P = 0.005; prolactin, P = 0.001). In multivariate analysis, besides Dukes stage, circulating prolactin emerged as the most significant independent prognostic factor influencing overall survival. Preoperative prolactin levels showed excellent significant correlation with response to therapy and progression of disease. A significant tenfold higher mean concentration of prolactin was observed in tumor-draining venous blood than in peripheral blood (P = 0.0001). Diffuse cytoplasmic staining for prolactin was seen in 51 percent (50/98) of the colorectal carcinomas. Prolactin messenger ribonucleic acid expression was seen in 88 percent (44/50) of the colorectal carcinomas. Sequence analysis of the 234-bp prolactin amplimer revealed that the sequence was homologous to exon 5 of pituitary prolactin messenger ribonucleic acid.

CONCLUSION

These multiple approaches confirmed that prolactin is produced by colorectal carcinoma cells. Looking at its prognostic value and correlation with disease activity, it may provide new insights into treatment for patients with colorectal carcinoma.

Prolactin as a local growth promoter in patients with locally advanced tongue cancer: GCRI experience

BACKGROUND

The purpose of this study was to assess the role of prolactin (PRL) in men with locally advanced tongue cancer.

METHODS

Circulating PRL was assayed immunoradiometrically in pretherapeutic and sequential blood samples of 99 patients with locally advanced tongue cancer. Patients were followed for 3 years or until their death within a stipulated time. Immunohistochemical localization of PRL was performed on formalin-fixed paraffin-embedded tissue sections. Tumoral prolactin receptors (PRLR) were estimated by ligand binding assay; the expression of PRL mRNA and PRLR mRNA were carried out by reverse transcriptase polymerase chain reaction (RT-PCR). Furthermore, PRL amplimer was sequenced and compared with human pituitary PRL amplimer.

RESULTS

Pretherapeutic PRL levels were significantly higher in patients with locally advanced tongue cancer compared with controls (p =.01). Thirty-four percent (34 of 99) of the patients had hyperprolactinemia (PRL >/=15.0 ng/mL). Univariate survival analysis showed that patients with pretherapeutic hyperprolactinemia had a significantly shorter overall survival than patients with pretherapeutic PRL <15.0 ng/mL serum (p =.0009). In multivariate analysis, PRL emerged as the most significant independent prognostic factor influencing overall survival. Furthermore, changes in serial PRL levels showed excellent correlation with response to therapy and progression of disease. Forty-four percent (24 of 54) of the tumors showed positive immunoreactivity with PRL antibody, indicating that PRL or a molecule similar to it is produced by tongue tumors. PRL mRNA expression was seen in 85% (43 of 50) of the tumors and confirmed the de novo synthesis of PRL. Sequence analysis of the 234 bp PRL amplimer revealed that the sequence was homologous to exon 5 of pituitary PRL mRNA. The action of PRL is mediated by PRLR, and it was observed that the PRLR positivity by ligand binding assay was 33%. The expression of PRLR mRNA by RT-PCR showed two forms of PRLR mRNA (ie, intermediate form [500-600 bp] seen in 82% (41 of 50 ) of the tumors and the long form [800-900 bp] seen in 36% (18 of 50) of the tumors. In 82% (41 of 50) of the tumors, either the intermediate or long form was seen.

CONCLUSIONS

This multifaceted study of PRL suggests that tongue cancer cells produce PRL, and this ectopically produced PRL might be acting as a major local growth promoter by means of autocrine and paracrine mechanisms. Looking at its prognostic value and correlation with disease activity, it may provide new insights into treatment of tongue cancer.

Lack of association between hyperprolactinemia and colon carcinoma

Two recent studies reported that many patients with colorectal carcinoma have elevated serum prolactin (PRL) concentrations and have suggested ectopic PRL secretion as the cause. In the present study, serum PRL was minimally elevated in 16 of 116 colon cancer patients and 2 of 25 control subjects; medications or chemotherapy appeared to be responsible for the PRL elevations in 11 of 16 cancer patients. Serum PRL was not correlated with either plasma carcinoembryonic antigen or disease stage. Preoperative and postoperative serum PRL concentrations were similar in 26 evaluated patients. None of 19 colorectal tumors was positive for PRL staining by immunohistochemistry. Thus, we could not confirm previous reports of frequent hyperprolactinemia in patients with colorectal cancer; factors such as medications, anxiety, pain, and nausea may have raised serum PRL in these earlier studies. Serum PRL is not a useful marker for colon carcinoma, at least in patients in the United States.

Medical treatment of prolactinomas

Prolactinomas are a common cause of reproductive and sexual dysfunction. Once other causes of hyperprolactinemia have been excluded with a careful history, physical examination, routine chemistries, and a TSH, MR imaging or computerized tomography will delineate the size and extent of the tumor. Medical therapy is the initial treatment of choice. When infertility is the primary indication for treatment, bromocriptine use has an extensive safety experience and is preferred. For other indications, however, cabergoline appears to be more efficacious and better tolerated. Transsphenoidal surgery remains an option, especially for patients with microadenomas, when medical therapy is ineffective.

Plasma prolactin in patients with colorectal cancer. Value in follow-up and as a prognosticator

BACKGROUND

Preoperative plasma prolactin and carcinoembryonic antigen (CEA) levels were assessed to monitor disease recurrence and to identify low-risk and high-risk patients with Dukes B or C colorectal cancer.

METHODS

Prolactin and CEA were estimated by radioimmunoassay method. Blood samples were collected preoperatively and sequentially thereafter from patients with colorectal cancer (N = 114); the samples were compared with samples from age-matched healthy control subjects (smokers and nonsmokers, N = 45). For rest of the analysis, patients with Dukes A disease (N = 7) were not included because of the small number. In monitoring recurrences, the criteria for positive test for the two markers was a continual increase in the marker level after an initial decrease or persistent high level of the marker. These were the indicators of relapse or no response to treatment. To determine the efficacy of the preoperative markers, the patients were grouped according to disease status at the end of 3 years, i.e., patients who had response to the treatment modalities (N = 52) and patients who later had progressive disease (N = 55). To determine the prognostic significance of preoperative marker levels, the patients were divided according to the cutoff levels (upper normal limits); for prolactin the cutoff level was 20.0 ng/ml plasma, and for CEA it was 5.0 ng/ml plasma.

RESULTS

Both of the markers were significantly high in patients with colorectal cancer compared with the markers of their respective control subjects (P < 0.0001). In monitoring disease course, the predictive power of prolactin was 100%, whereas that of CEA was 66%. Prolactin showed a lead time of 2-3 months. Preoperative prolactin levels were significantly higher in patients who later had progressive disease (P < 0.001) than in patients who had response to the treatments. However, such an intergroup variation was not observed for CEA. Patients with preoperative levels of prolactin greater than 20.0 ng/ml had shorter overall survival times than did those with prolactin levels less than 20.0 ng/ml plasma; such a trend was not observed for patients with CEA levels less than 5.0 ng/ml and those with CEA levels greater than 5.0 ng/ml plasma.

CONCLUSION

Prolactin is a better overall marker than is CEA in patients with Dukes B or C colorectal cancer. The authors recommend the use of plasma prolactin levels to help identify low-risk and high-risk patient subgroups so that high-risk patients may be followed up more intensely and treated accordingly. Hyperprolactinemic patients with Dukes B or C disease have shortened survival time.

Use of serum prolactin for monitoring the therapeutic response in ovarian malignancy

Serum prolactin level was estimated in 20 women with ovarian malignancy. High prolactin level was observed in 13 out of 20 women. However, no correlation was seen between prolactin level and the stage of the disease. Serial measurement of prolactin showed a correlation of prolactin level with tumor mass in three patients in which serial tumor mass volume measurements were available. A rise in serum prolactin level was observed in women who had recurrence of the disease. Although the current study is based on a relatively small number of patients, it may be concluded that serum prolactin level might be used as a tumor marker to monitor the therapeutic response in cases of ovarian malignancy.

Ectopic prolactin secretion from a gonadoblastoma

A 6.5-year-old girl developed isosexual, pseudoprecocious puberty secondary to a gonadoblastoma. The tumor was found to produce and secrete both immunoassayable and bioassayable prolactin based on immunohistochemical techniques and the presence of a prolactin gradient between the tumor vein and peripheral vein. The source of the prolactin was a Sertoli-like cell. Neither growth hormone nor growth hormone-releasing hormone was detected within the tumor. This case confirms the ectopic production of prolactin by neoplastic tissue.