Prolactinomas

1. Prolactinomas Yona Greenman MD Institute of Endocrinology and Metabolism Tel Aviv-Sourasky Medical Center

2. Issues • Diagnosis • Macroprolactin • Hook effect • Treatment • Long term follow up • Discontinuation of treatment • Pregnancy

3. Prolactin • Human PRL is synthesized as a prehormone of 26 kDa. Preprolactin is cleaved into a 199 a.a. peptide with a molecular weight of 23 kDa • This monomeric form accounts for 85% of circulating PRL in both normal and hyperprolactinemic sera • Big PRL (50 kDa), a covalently bound dimer of PRL accounts for 10-15% of total PRL • Big Big PRL (>150 kDa) or macroprolactin • Post-translational modifications of PRL (glycosylated an phosphorylated variants), and 14, 16 and 22 kDa proteolysed forms

4. Macroprolactin • Macroprolactin is a macromolecular complex of monomeric PRL and an immunoglobulin, generally an IgG antibody • Reduced clearance of this complex accounts for persistent hyperprolactinemia • The macroprolactin complex is confined to the intravascular space, has limited bioavailability, hence its reduced bioactivity

5. Clinical Features • It is present in significant amounts in up to 24 % of hyperprolactinemic sera • Often the condition is identified serendipitously, in the absence of classic symptoms of hyperprolactinemia • Symptoms leading to the measurement of prolactin, such as menstrual disorders, galactorhea or various degree of infertility, are not specific, and may occur coincidentally in macroprolactinemic patients • High prevalence of pituitary lesions identified incidentally by imaging procedures may coexist with macroprolactinemia

6. Clinical Diagnosis • Differentiation of macroprolactinemic patients from those with true hyperprolactinemia on clinical grounds is unreliable • The percentage of clinically significant hyperprolactinemic samples explained by hyperprolactinemia is similar across all levels of total prolactin Gibney et al (2005) J Clin Endocrinol Metab 90:3927-3932 .

7. The Macroprolactin Problem • Misdiagnosis of hyperprolactinemia may result in unnecessary diagnostic procedures and inappropriate treatment • Recognition of macroprolactin and the “pseudohyperprolactinemia” affords the opportunity to make a correct diagnosis of the patient’s clinical condition

8. Clinical Question Should every hyperprolactinemic serum be screened for macroprolactin?

9. Identification of Macroprolactin by Gel Chromatography A- First peak (69%)- big-big PRL (fractions 15–23; molecular mass >100 kDa); Second peak (15%)- big PRL (fractions 27–31; 50 kDa); Third peak (16%) -monomeric PRL (fractions 33–39; 23–25 kDa) B- Monomeric PRL secreted by the tumor in vitro Vallette-Kasic et al JCEM (2002) 87: 581-588

10. PEG Precipitation • Prolactin recovery < 40% after PEG consistent with macroprolactinemia • Prolactin levels fall within the normal range following removal of macroprolactin by PEG (because there is coprecipitation of monomeric PRL by PEG, values obtained by treating normal serum are used as reference) Gibney et al (2005) Clin Endocrinol62 (6), 633-643.

11. Detection of Prolactin in Serum Containing Macroprolactin Smith et al (2002) J Clin Endocrinol Metab 87: 5410-5415

12. Is macroprolactin just a laboratory artifact that should be dismissed? 1) Possibility that macroprolactin has some biological activity, or maybe if functions as a pool of monomeric prolactin that intermittently dissociates from the low affinity high capacity IgG complex, thus causing symptoms of prolactin excess. -Calls for assays able to detect macroprolactin 2) Macroprolactin is asymptomatic and causes diagnostic confusion - Calls for assays that do not recognize macroprolactin

13. Each center must know the specific characteristics of the prolactin immunoassay they use. For confirmation of macroprolactinemia, polyethylene glycol precipitation is the most practical method. Conclusions

14. Conclusion There is no consensus as to whether macroprolactin should be looked for in sera of all hyperprolactinemic patients.

15. Hook Effect • High amount of circulating PRL causes antibody saturation in the immunoradiometric assay, leading to artifactually low results • Giant macroprolactinomas • Patients undergo surgery because of an initial diagnosis of non-functioning tumors • Hint for diagnosis- elevation of prolactin levels after surgery, pathology ICH

16. *Prolactin levels after dilution: 317520-950000 mU/l St-Jean et al, Clin Endocrinol (1996) 44:305-309

17. Immunoassays • Immulite 2000 immunometric assay performance data: • High dose hook effect: none up to 20,500 ng/ml (434,600 mU/l) • Other assays?

18. Conclusions • To overcome the hook effect, an immunoradiometric PRL assay should be performed with serum dilution at 1:100 • The hook effect should be excluded in new patients with giant pituitary macroadenomas who have mildly elevated PRL levels

19. Surgery • Microprolactinoma • Normoprolactinemia in 71 % of cases • Recurrence rate of 17 % • Long term cure rate of 59 % • Macroprolactinoma • Initial normoprolactinemia in 32 % of cases • Long-term cure inn 26 %

20. Surgery About 10 percent of patients may require surgery: • Resistance to dopamine agonist therapy • Visual field deficits do not improve with medical therapy • Apoplexy with neurological signs • Cystic macroprolactinomas that in general do not respond well to dopamine agonist treatment • Intolerance to dopamine agonists

21. Medical Treatment • Drug of choice • For how long? • Discontinuation of treatment • Long term follow up

22. Medical therapy • Large comparative studies of cabergoline and bromocriptine have convincingly demonstrated the superiority of cabergoline in terms of tolerability, patient convenience, decreasing prolactin secretion, restoration of gonadal function, and reduction of tumor volume. • Although cabergoline is more effective, bromocriptine has been used satisfactorily for years, and, being less expensive, should be considered in medical systems with strong budget constraints.

23. Does the Initial Choice Affect Outcome? • The prevalence and extent of macroprolactinoma shrinkage after cabergoline treatment is higher in naive patients • These results suggest the use of cabergoline as first line in macroprolactinoma Colao et al, J Clin Endocrinol Metab (2000) 85:2247-2252

24. Natural History of Prolactinomas • Less than 5% of microprolactinomas progress in the long term to macroprolactinomas • Hyperprolactinemia resolves spontaneously in about 30% of microadenomas (mainly with menopause or post-pregnancy) Schlechte et al, JCEM (1989) 68:412 Karunakaran et al, Clin Endocrinol (2001) 54:295

25. Treatment Withdrawal • In this study withdrawal was considered if prolactin levels were normal, if MRI showed no tumor or a 50% size reduction, with a minimum distance of 5 mm from optic chiasm • Minimal treatment period of 24 months • 25 non-tumoral hyperprolactinemia ,105 microprolactinomas, 70 macroprolactinomas Colao, A. et al. NEJM (2003) 349:2023

26. Recurrence (Elevation of PRL) • 78% of macroprolactinomas with residual tumor on MRI at the time of treatment withdrawal • 33% of macroprolactinomas with normal MRI at the time of treatment withdrawal • 42% of microprolactinomas with positive MRI • 26% of microprolactinomas with negative MRI

27. 14-yr-old girl harboring a MAC. A, Before treatment, B, 2 months on BRC; C, 8 months on BRC; D, 16 months after BRC withdrawal Colao et al. NEJM (2003) 349:2023 Passos et al, JCEM(2002) 87: 3578

28. Conclusions • If a patient has normal PRL levels after therapy with dopamine agonists for at least 3 years and the tumor volume is markedly reduced, a trial of tapering and stopping these drugs may be initiated •   Such patients need to be followed carefully to detect recurrence of hyperprolactinemia and tumor enlargement so that treatment can be resumed

29. Pregnancy • Microadenomas- risk for adenoma growth during pregnancy appears to be 1-2 % after drug discontinuation • Macroadenomas- 23% risk of tumor enlargement • Pre-pregnancy debulking of macroprolactinoma- 2.8% risk of tumor enlargement Molitch M. J Reprod Med (1999) 44:1121

30. Pregnancy- microprolactinoma • Dopamine-agonists can be safely stopped in patients with microprolactinomas as soon as pregnancy has been confirmed. • Patients should be advised to report for urgent assessment in in the event of severe headaches or visual disturbances. • Serial PRL determinations are not necessary

31. Pregnancy- Macroprolactinoma Options for such women include stopping the dopamine agonist when pregnancy is confirmed with close surveillance or continuing the dopamine agonist through the pregnancy

32. Pregnancy- Macroprolactinoma • Debulking surgery before pregnancy in women with macroprolactinomas to reduce the likelihood of major tumor expansion, is a less preferable option, as medical therapy during pregnancy is probably less harmful than surgery • If the enlarged tumor does not respond to reinstitution of dopamine agonist therapy, alternatives include delivery if the pregnancy is far enough advanced, or transsphenoidal surgery

33. Lactation   Women wishing to breast-feed their infants should not be given dopamine agonists as this will lower PRL levels and impair lactation. There are no data to suggest that breast-feeding may cause an increase in tumor size