Decreased dopaminergic tone and increased basal bioactive prolactin in men with human immunodeficiency virus infection

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Abstract
OBJECTIVE The aims of the study were: (1) to assess dopaminergic tone in a group of HIV infected men and the bioactivity and the molecular species of their circulating PRL in comparison with healthy men and (2) to search for a correlation between serum PRL and CD4+ T lymphocytes and viral load. DESIGN In a cross-sectional study the effect of acute dopaminergic blockade with intravenous metoclopramide on serum PRL (both immunoreactive and biologically active), TSH and PRL circulating molecular isoforms was evaluated. PATIENTS Twenty untreated HIV infected men category C2 or C3, mean (SD) age 26·9 (6·3) years, were compared to 14 clinically healthy HIV-negative men, age 25·4 (2·3) years. MEASUREMENTS Under fasting conditions and following metoclopramide administration duplicate measurements of serum immunoreactive PRL, bioactive PRL (PRL dependent Nb2 lymphoma cell assay) and immunoreactive TSH were performed. The molecular species of circulating PRL were determined by immunoblot analysis, CD4+ T lymphocytes by flow cytometry and the viral load using a nucleic acid sequence-based amplification assay. RESULTS In HIV infected men fasting bioactive (but not immunoreactive) PRL was higher (P = 0·03), but the stimulated PRL (both immunoreactive and bioactive) was lower than in healthy men throughout the test (P ≤ 0·01). Fasting serum TSH was similar in HIV-infected and healthy men while its response to metoclopramide was absent in the former but not in the latter (P = 0·049). A 23·5-kD PRL was the predominant circulating isoform both in patients and healthy men. Considering HIV-infected and healthy men, CD4+ T lymphocytes correlated negatively with fasting bioactive PRL (P = 0·008) and positively with the area under the PRL (both immunoreactive and bioactive) curves (P < 0·001). The viral load was negatively correlated with the area under the curve of the bioactive/immunoreactive ratio (P = 0·008). CONCLUSIONS The raised fasting bioactive PRL, the diminished response of both immunoreactive and bioactive PRL and the absent TSH response to metoclopramide in HIV infected men, suggest the existence of a decreased, but not absent dopaminergic tone. A monomeric form of PRL was the predominant circulating species, as in healthy men, and this hormone seems to be associated both with CD4+ T lymphocytes and the viral load.