Minimizing Matrix Effects for the Accurate Quantification of 25-Hydroxyvitamin D Metabolites in Dried Blood Spots by LC-MS/MS.

Background: The noncalcemic actions of vitamin D in multiple organs are now widely recognized. Vitamin D status has been linked with a wide variety of conditions, which has led to an increasing demand for vitamin D screening. In particular, there is intense interest in the impact of vitamin D on a variety of developmental conditions.

Distribution of 25-hydroxyvitamin D3 in dried blood spots and implications for its quantitation by tandem mass spectrometry.

Dried blood spots (DBS) are a convenient collection and archiving method for blood specimens. The interest in screening certain analytes in neonatal DBS continues to increase for a variety of paediatric disorders. 25-Hydroxyvitamin D(3) (25OHD(3)) is one such analyte.

Decreased androgen receptor levels and receptor function in breast cancer contribute to the failure of response to medroxyprogesterone acetate.

Previously, we reported that androgen receptor (AR), but not estrogen receptor (ER) or progesterone receptor (PR), is predictive of response to the synthetic progestin, medroxyprogesterone acetate (MPA), in a cohort of 83 patients with metastatic breast cancer. To further investigate the role of AR in determining response to MPA in this cohort, we analyzed AR levels by immunohistochemistry with two discrete antisera directed at either the NH2 or the COOH termini of the receptor. Compared with tumors that responded to MPA (n = 31), there was a significant decrease in the intensity and extent of AR immunoreactivity with both AR antisera in tumors from nonresponders (n = 52).