The inverse relationship between zinc (Zn++)
and prolactin (PRL) was detected in in vitro studies,
whereas in vivo results are contradictory. In order to evaluate this controversial subject we
studied patients with hyperprolactinemia. Basal serum Zn++
levels and serum PRL response to
acute and chronic oral Zn++ administration were evaluated in seven patients with prolactinomas
and one with idiopathic hyperprolactinemia. Serum PRL levels did not change after acute oral
Zn++ administration (37.5 mg), although Zn++
levels increased from 1.11±0.15
to 2.44±0.39 μg/mL(P<0.05)
. Zn++ administration (47.7 mg daily) during 60 days increased serum Zn++ levels
from 1.11 ± 0.15 to 1.59 ± 0.58 μg/mL (p < 0.05) but caused no change in serum PRL levels. The
TRH tolerance test (200 μg
) was performed before and after 60 days of Zn++
administration, and
PRL response to TRH was unchangeable and similar in both tests. We concluded that acute or
chronic Zn++
administration does not inhibit PRL secretion in basal condition or by TRH effect in
hyperprolactinemic patients.
