Pituitary and Placentally Derived Hormones in Cerebrospinal Fluid during Normal Human Pregnancy*

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Abstract
To examine the potential routes by which placental and pituitary hormones gain access into the cerebrospinal fluid (CSF), normal pregnant women had CSF and blood samples collected after admission to the hospital before delivery. CSF and serum samples, obtained before CSF collection, were examined for PRL, βhCG, and human placental lactogen (hPL). Mean values (±SE) in serum were 5757 ± 815 mlU/ml for βhCG and 22.4 ± 2.42 mlU/ml for CSF, and the serum to CSF ratio was 289 ± 28 in 26 samples in which these parameters were simultaneously measured. Mean serum hPL was 15.3 ± 1.15 fig/ml, and CSF hPL was 0.565 ± 0.048 fig/ml; the serum to CSF ratio from 22 subjects was 22.7 ± 2.32, which was significantly different from the serum to CSF ratios for βhCG and PRL. Serum PRL values were 182.6 ± 17.3 ng/ml, and CSF values were 15.36 ± 1.33 ng/ml; the serum to CSF ratio from 32 subjects was 10.7 ± 1.33, which was lower than the ratio for either)8hCG or hPL. Regression analysis of the simultaneously determined serum and CSF hormone levels, using several curve-fitting equations, revealed a heterogeneity of regressions for the different hormones. β-hCG could best be described by a linear regression analysis, and the correlation co'efficient was highly significant (r = 0.84; P < 0.001). hPL was best described by a polynomial regression with a highly significant correlation (r = 0.82; P < 0.005). In contrast, PRL levels in serum and CSF were not correlated (r = 0.3; P > 0.05), and several regression analyses failed to demonstrate a relationship between the two parameters. This study has defined the range of serum and CSF βhCG, hPL, and PRL expected in term pregnant women without endocrine or neurological disease. Serum to CSF ratios and regression analyses of these values for βhCG, hPL, and PRL indicated a heterogeneity of potential CSF access for these three peptide hormones. The data were most compatible with the concept that βhCG gains access to the CSF by a process of simple diffusion, and that hPL may gain access by a facilitated process. However, PRL access to CSF appeared to be independent of circulating levels of this hormone in term pregnant women. Also, the low serum to CSF ratio for PRL indicates that this hormone in term pregnant women reaches CSF by a more direct route than from passage across the blood-CSF barrier.