Plasma homovanillic acid and prolactin in systemic lupus erythematosus

Abstract

Prolactin (PRL) is an important immunoregulator and might have a role in the pathogenesis of systemic lupus erythematosus (SLE). The regulation of pituitary prolactin secretion is complex and involves a negative feedback process in the hypothalamus, in which dopamine plays the principal role. However, the main source of serum prolactin in lupus patients is still not clearly established. Since homovanillic acid (HVA), the principal metabolite of dopamine (DA), is removed from the brain into the blood, it would indirectly reflect DA metabolism. It is assumed that the turnover of a neurotransmitter can be determined through an analysis of its metabolites. The objective of this study was to analyse plasma samples from SLE patients to see if there were any alterations in neurally functioning DA through its principal metabolite, HVA. We also measured the levels of PRL and compared HVA and PRL with the clinical activity of the disease. Twenty-four SLE patients and fifteen healthy controls were studied. The investigation was done over a period of 3 months. The results of this study show significantly low levels of HVA in lupus patients compared to controls (P < 0.0001). This corresponds to a decrease in dopamine turnover. Hyperprolactinemia was observed in nine patients, and the average level of prolactin in lupus patients was higher than in healthy controls (P < 0.001). For the duration of the study, a significant percentage of variation was observed in the levels of HVA in the clinically active patients (P < 0.05) compared to inactive patients. When PRL was compared in these groups, throughout the study, no significant percentage of variation was observed. The relationship between HVA and PRL in healthy controls was r = 0.47, P = 0.08, and in patients was r = 0.04, P = 0.84. It is suggested that there is a probable association between plasma levels of HVA and PRL in the healthy controls and not in the SLE patients.

Sex hormones and systemic lupus erythematosus: Review and meta‐analysis

“…Estradiol stimulates prolactin secretion, and prolactin suppresses gonadal steroid synthesis (69,70). As shown in Table 4 and Figure 4, several studies have examined the relationship of prolactin and SLE in adults, comparing either the mean concentrations in patients with those of controls or normal and abnormal prolactin concentrations (hyperprolactinemia), with or without a control population (71)(72)(73)(74)(75)(76)(77)(78)(79)(80)(81)(82)(83)(84)(85)(86)(87). Seven of 10 female-only and 2 of 4 male-only SLE studies showed significantly increased serum prolactin concentrations in adult lupus patients compared with controls.…”

“…Other possibilities include cytokine-stimulated pituitary prolactin release (54,55), production of immunoreactive prolactin peripherally (98,99), or aberrant pituitary prolactin secretion in lupus patients (74,75). Some of these explanations are, however, superficially not compatible with the other steroid hormone abnormalities seen in female SLE patients.…”

Plasma catecholamine metabolite levels and the activities of psychiatric symptoms in systemic lupus erythematosus

“…Previous reports have demonstrated that plasma HVA levels in SLE patients are lower than those in healthy controls (Ferreira et al ., ). Another report showed that noradrenaline and dopamine plasma levels were increased in a patient with overlapping SLE and polymyositis syndromes (Nakajima et al ., ).…”

Prolactin, a pituitary hormone that modifies immune responses

“…Papers presented at the 5th International Conference on SLE suggested that changes in dopaminergic tone, 59 antibodies to prolactin, 60 or dysfunction of the hypothalamic-pituitary-glucocorticoid axis 61 occur in SLE. It should be noted, however, that one study presented in this issue showed that lupus patients with relatively inactive SLE may have normal hypothalamic-pituitary responses.…”