Endocrine Abstracts

The blood-brain barrier for peptide hormones is protective for the maternal brain.

OBJECTIVE: To compare peptide hormone levels on the two sides of the blood cerebrospinal fluid barrier in pregnant, non pregnant and menopausal women.

METHODS: We investigated, with the approval of the local ethics committee, 35 healthy pregnant women at term, aged 21-41 years (group G), 27 non-pregnant women aged 21-43 years (group C) and 15 menopausal women aged 48- 70 years (group M). Prolactin (PRL), TSH, insulin and estradiol were measured by immunochemoluminiscence in blood and cerebrospinal fluid(CSF) sampled simultaneously before rachianestaesia for caesarean section or for abdominal surgery.

RESULTS: Prolactin CSF level increases in pregnancy, i.e. group G (6.8plus/minus2.4 nanograms per milliliter) compared to other groups (group C: PRL CSF 1.7plus/minus0.8, group M: PRL CSF 1.1 plus/minus0.5, p:0.0001). However the CSF/serum ratios are similar (p:ns). TSH CSF significantly increases in gestation (p:0.01) compared to both non-pregnant and menopausal women, i.e. group G 0.43microUI per milliliter (0.1- 1.01), group C 0.08microUI per milliliter (0.01- 0.14) and group M 0.05 microUI per milliliter (0.02- 0.09). However, the serum TSH in pregnancy is similar with the groups C and/or M (p:ns). Total thyroxin increases in serum, but not in CSF during pregnancy. Insulin levels are significantly lower in CSF during pregnancy compared to groups C and M. CSF/serum ratios are 0.26 plus/minus0.07 in group G, 0.43plus/minus0.06 in group C, and 0.44plus/minus0.08 in group M (p:0.05). As there is no BCB for estradiol we found an elevated CSF level parallel to high serum levels.

CONCLUSION: The blood-CSF barrier is selectively modified during pregnancy, more permeable for TSH, less for insulin, and unchanged for prolactin and thyroxin. The mechanism is not clarified but the high estradiol level might be involved.