Correlation between Systemic Lupus Erythematosus Activity and Plasma Levels of Monomeric Prolactin and Macroprolactin

The correlation of prolactin (PRL) levels with SLE activity is a controversial issue, which could be explained by the presence of macroprolactin (MPRL), a high molecular weight form of PRL with a lower in vivo biological activity.

We aimed to evaluate the prevalence of hyperprolactinemia, PRL and MPRL levels in SLE patients, and to correlate these levels with disease activity as measured by the SLE Disease Activity Index (SLEDAI).

We conducted a case-control, cross-sectional study with 73 SLE patients (L group), sixty-two of which were evaluated before and after treatment, and correlated the results with serum PRL and MPRL levels. These results were compared to those of 29 healthy women with ovulatory cycles (C group) and 34 women in the third trimester of pregnancy (G group).

Mean PRL levels were: 8,8 ng/ml on C group; 12,0 ng/ml on L group (p = 0.02) and 158,5 ng/ml on G group. Hyperprolactinemia was present in 19.4% of SLE patients, but was not found on C group. The MPRL form was predominant among 20.5% of SLE patients, in none of the C group and in only 5.8% of pregnant women. There was a strong correlation between the PRL levels and SLE activity, regardless of the hormone's molecular form. SLE treatment was able to reduce levels of all forms of PRL. The predominance of MPRL, however, did not change after treatment.

Despite its lower biological activity, MPRL levels correlated with LES activity as much as free prolactin.