Effect of vitamin B6 on the serum concentration of pituitary hormones in normal humans and under pathologic conditions.

Abstract

The effect of the acute intravenous administration of B6(300 mg pyridoxine chloride and 10 mg pyridoxal 5 — phosphate) on the circulating levels of pituitary hormones was investigated in humans under normal and pathologic conditions. In normal subjects maximal changes expressed as per cent of the basal levels were as follows: 52% suppression of prolactin (PRL) at 90 minutes, 18% of TSH at 90 minutes and 315% stimulation of GH at 30 minutes. LH was also mildly suppressed (38%) at 60 minutes but there were no appreciable changes in serum FSH and Cortisol. The effect of Beon PRL and GH release was abolished after 3 day pretreatment with sulpiride; this finding suggests a dopaminergic mediation. In hypothalamo-pituitary diseases the response to Be was found altered: the inhibition of serum PRL was diminished in normo- or hyperprolactinemic women with galactorrhea and disturbed menses but without X-ray evidence of pituitary tumor. When PRL or GH secreting adenomas were present, the responses of PRL and GH to Be were absent or paradoxical. Our observations support the hypothesis that in normal subjects Be activates hypothalamic aromatic-L-aminoacid-decarboxylase with a consequent increase of dopamine concentration. The lack of response to Be observed in hypothalamo-pituitary disorders might be attributed either to an abnormal response of the pituitary to dopamine or to a reduced ability of the coenzyme to promote the synthesis of this neurotransmitter.