Hair cortisol is a measure of chronic or repeated hypothalamic–pituitary–adrenal axis activation in response to physical or psychological stressors. Hair cortisol has been successfully used as a measure of chronic stress in adults and children; however, its use as a valid measure in preterm infants has been limited by challenges in measuring cortisol in the low mass samples collectable from these infants.
The purpose of this report is to present a novel protocol for the measurement of hair cortisol in very low mass hair samples.
Small changes were made to previously published protocols. After washing and pulverizing the hair samples, a double methanol cortisol extraction was performed. Samples were spiked with a known quantity of cortisol and analyzed in duplicate using an enzyme-linked immunosorbent assay.
Hair cortisol was detectable in samples weighing between 0.4 and 10.9 mg. The mean cortisol level was 23.74 pg/mg hair (SD = 26.38).
With small changes to previously published laboratory protocols, cortisol is quantifiable in low mass hair samples from preterm infants. This technical advance is an important step toward quantifying the stress experiences of hospitalized preterm infants.