Prolactin and its response to the luteinizing hormone-releasing hormone thyrotropin-releasing hormone test in patients with endometriosis before, during, and after treatment with danazol

Prolactin and Hyperprolactinaemia in Endometriosis-Related Infertility: Are There Clinically Significant Connections?

Endometriosis and hyperprolactinaemia are conditions that might lead to infertility as a consequence. The aim of this article was to present the current knowledge about possible relationships between prolactin/hyperprolactinaemia and endometriosis-related infertility. Experimental studies on local prolactin acting as cytokine and relationship of prolactin and endometriotic tissue, as well as clinical studies on hyperprolactinaemia and endometriosis-related infertility suggest the possible role of prolactin in endometriosis-related infertility, but final proof is still missing and the exact pathogenesis of infertility in such cases is still under investigation. Novel strategies in the treatment of endometriosis-related infertility, based on its connection with prolactin such as the use of prolactin receptor antibodies and prolactin receptor antagonists, are under investigation, but adequate clinical studies have yet to be undertaken.

Prolactin and pain of endometriosis

Women experience chronic pain more often than men with some pain conditions being specific to women while others are more prevalent in women. Prolactin, a neuropeptide hormone with higher serum levels in women, has recently been demonstrated in preclinical studies to sensitize nociceptive sensory neurons in a sexually dimorphic manner. Dysregulation of prolactin and prolactin receptors may be responsible for increased pain especially in female predominant conditions such as migraine, fibromyalgia, and pelvic pain. In this review, we focus on the role of prolactin in endometriosis, a condition characterized by pelvic pain and infertility that affects a large proportion of women during their reproductive age. We discuss the symptoms and pathology of endometriosis and discuss how different sources of prolactin secretion may contribute to this disease. We highlight our current understanding of prolactin-mediated mechanisms of nociceptor sensitization in females and how this mechanism may apply to endometriosis. Lastly, we report the results of a systematic review of clinical studies conducted by searching the PubMed and EMBASE databases to identify association between endometriosis and blood levels of prolactin. The results of this search strongly indicate that serum prolactin levels are increased in patients with endometriosis and support the possibility that high levels of prolactin may promote pelvic pain in these patients and increase vulnerability to other comorbid pain conditions likely by dysregulating prolactin receptor expression. Targeting of prolactin and prolactin receptors may improve management of pain associated with endometriosis.

Peripheral biomarkers of endometriosis: a systematic review

BACKGROUND

Endometriosis is estimated to affect 1 in 10 women during the reproductive years. There is often delay in making the diagnosis, mainly due to the non-specific nature of the associated symptoms and the need to verify the disease surgically. A biomarker that is simple to measure could help clinicians to diagnose (or at least exclude) endometriosis; it might also allow the effects of treatment to be monitored. If effective, such a marker or panel of markers could prevent unnecessary diagnostic procedures and/or recognize treatment failure at an early stage.

METHODS

We used QUADAS (Quality Assessment of Diagnostic Accuracy Studies) criteria to perform a systematic review of the literature over the last 25 years to assess critically the clinical value of all proposed biomarkers for endometriosis in serum, plasma and urine.

RESULTS

We identified over 100 putative biomarkers in publications that met the selection criteria. We were unable to identify a single biomarker or panel of biomarkers that have unequivocally been shown to be clinically useful.

CONCLUSIONS

Peripheral biomarkers show promise as diagnostic aids, but further research is necessary before they can be recommended in routine clinical care. Panels of markers may allow increased sensitivity and specificity of any diagnostic test.

Aromatase expression in endometriotic tissues and its relationship to clinical and analytical findings

OBJECTIVE

To study the relationship between aromatase expression in endometriotic tissues and clinical and laboratory findings.

DESIGN

Prospective basic and clinical research.

SETTING

University hospital.

PATIENT(S)

Sixty-two women with endometriosis, and 12 without endometriosis.

INTERVENTION(S)

Conservative surgery, or hysterectomy and adnexectomy, along with an immunohistochemical study of aromatase in endometriotic and nonendometriotic tissues.

MAIN OUTCOME MEASURE(S)

Symptoms of the disease, ultrasound and surgical findings, values of tumor markers, steroids and immunoglobulins, and recurrences after surgery.

RESULT(S)

We observed positive immunohistochemical expression for aromatase in endometriotic tissues from 38 patients (61.3%). Aromatase expression was negative in the rest of the tissues studied and in the 12 cases without endometriosis. Aromatase-positive patients had a higher number of endometriomas, more bilaterality, and more moderate-to-severe chronic pelvic pain. Also, infertility and associated leiomyomas were more frequent in these patients, though without significant differences. There were no differences in recurrence of the disease 1 year later. Estradiol and PRL levels were significantly higher, and IgG values lower, than in aromatase-negative patients. High values of blood sedimentation rate were more frequent in aromatase-negative patients.

CONCLUSION(S)

Molecular alterations such as the presence of aromatase in endometriotic tissues could be involved in the development or maintenance of endometriosis. Our findings suggest major severity, activity, and chronic pelvic pain in patients with aromatase in endometriotic tissue.

Prolactin secretion in endometriotic patients

OBJECTIVE

To clarify a significance of prolactin (PRL) for infertility in endometriosis.

STUDY DESIGNS

For seventy endometriotic patients with or without infertility, serum PRL concentrations measured by radioimmunoassay before and 30 min after 500 micrograms of thyrotropin-releasing hormone (TRH) injection were analyzed in relation to the Revised American Fertility Society score in endometriosis as well as to the outcome of the treatment for endometriotic infertility.

RESULTS

While no significant relationship was found between the basal PRL levels and the stage of endometriosis or the outcome of the treatment for infertility, the PRL value after TRH injection was significantly greater in the patients who did not become pregnant than those who did (P < 0.05).

CONCLUSIONS

Occult hyperprolactinemia may be involved in infertility in endometriotic patients.

Relationship between 17-beta-estradiol and prolactin in the regulation of natural killer cell activity during progression of endometriosis

Endometriosis is an estrogen-dependent disease affecting women during their reproductive years. An abnormal immune function and, in particular, a decreased natural killer (NK) cell activity have been found in endometriosis, suggesting a role of the immune system in the pathophysiology of the disease. We have recently evidenced a significant inverse relationship between 17-beta-estradiol plasma levels and NK cytotoxicity in endometriosis patients. In this study we have investigated the combined role of 17-beta-estradiol (E2) and prolactin (PRL) in the regulation of NK cell activity during the progression of endometriosis, by evaluating the correlation among E2, PRL, and other immunomodulating neurohormones on both the cytotoxic activity and the number of NK cells in women at different stages of endometriosis. The early stages (I/II) of endometriosis are characterized by increased plasma levels of either E2 or PRL without significant alterations of NK cell activity in comparison with healthy subjects. The progression to advanced stages (III/IV) of the disease is associated with a further increase of E2 levels, a decrease of PRL plasma concentrations (with an increase of E2/PRL ratio), and an impairment of NK cytotoxicity. The plasma levels of both E2 and PRL and the E2/PRL ratio are significantly correlated with the values of NK cytotoxicity in advanced stages of endometriosis. Either the absolute number or the relative percentage of CD16+ or CD56+ peripheral lymphocytes are not significantly different between patients at either stages I/II or III/IV and healthy controls. Plasma levels of progesterone (P) and luteinizing hormone (LH), are not significantly changed in different stages of endometriosis with respect to healthy controls. The significant decrease of follicle-stimulating hormone (FSH) plasma levels found in either stages I/II or III/IV endometriosis patients is not correlated with the NK cell activity. In conclusion, at advanced stages of endometriosis the impairment of NK cell activity occurs with increased E2, and decreased PRL plasma levels. Additional studies are required to determine whether the E2/PRL ratio represents a possible biochemical marker of endometriosis.

Luteal function in infertile patients with endometriosis

OBJECTIVE

Our purpose was to determine whether infertile patients who have endometriosis show luteal phase defects.

STUDY DESIGN

The luteal function in 24 infertile patients who had endometriosis was compared with the luteal function in 20 patients who had unexplained infertility and did not have endometriosis (control). In both groups serum luteinizing hormone, follicle-stimulating hormone, progesterone, and estradiol were assayed every day throughout the menstrual cycle. Endometrial biopsy specimens were obtained from eight patients of the endometriosis group for histologic dating of the endometrium.

RESULTS

No significant differences in progesterone levels were observed between these two groups during the mid and late luteal phase. Seven of the eight patients who underwent histologic dating showed a luteal phase pattern, whereas only one patient was out of phase.

CONCLUSION

Infertile patients who have endometriosis do not always have luteal phase defects.

Provocative tests of prolactin before, during and after long-term danazol treatment in patients with endometriosis

Ten patients suffering from endometriosis were treated with danazol at a dose of 200 mg three times daily for 6 months. To evaluate prolactin secretion, a thyrotropin releasing hormone (TRH) test and an insulin challenge test were carried out in the follicular phase before treatment, during the 6th month of treatment and after the reappearance of the second menses. The same tests were also performed, only once, in the follicular phase of ten normal women. The absence of a significant difference in basal prolactin levels as well as the response to the TRH and insulin challenge tests between controls and patients with endometriosis, before and after danazol treatment, support the view that hyperprolactinemia should not be considered as a cause of infertility in endometriotic women. Furthermore, the significant reduction of prolactin response to provocative tests during danazol treatment may be associated with the low estrogen levels caused by the medication. Finally, the inadequate prolactin response to insulin-induced hypoglycemia in patients with endometriosis and in normal women shows that this provocative test is not so effective for hypothalamic stimulation of prolactin.