Estradiol

At each visit, blood samples were collected and frozen (−70˚C) before analysis with standard immunoassay kits for follicle-stimulating hormone (FSH, IU.l⁻¹) (Siemens Healthcare Diagnostics, Los Angeles, CA, USA; intraassay and interassay coefficients of variations were 2.6% and 5.5%, respectively; sensitivity, 0.1 IU.l⁻¹), progesterone (ng.ml⁻¹) (Siemens Medical Solutions Diagnostics, Los Angeles, CA, USA; intraassay and interassay coefficients of variations were 4.0% and 5.7%, respectively; sensitivity, 0.2 ng.ml⁻¹) and estradiol (pg.mol⁻¹) (Beckman Coulter Inc., Fullerton, CA, USA; intraassay and interassay coefficients of variations were 6.7% and 7.6%, respectively; sensitivity, 3 pg.mol⁻¹). progesterone levels ≥3 ng.ml⁻¹ were used as a cut-off to classify the luteal phase^{46 (link)} (five women with and five women without insomnia had a PSG night recorded in the luteal phase of their menstrual cycles; in all the remaining nights progesterone was <3 ng.ml⁻¹).

The following analytes were measured according to the manufacturer's specifications: triglycerides (#T7532-120, Fisher Scientific, VA), cholesterol (#T7-120, Fisher Scientific, VA), alanine aminotransferase (ALT) (#A7526-150, Fisher Scientific, VA), aspartate aminotransferase (AST) (#A7561-150, Fisher Scientific, VA), leptin (#MOB00, R & D System, Minneapolis, MD), estradiol (#DSL- 4800, Beckman Coulter, Danvers, MA), testosterone (#DSL- 4900, Beckman Coulter, Danvers, MA), insulin (#80558, Crystal Chem, Downers Grove, IL) and progesterone (#90060, Crystal Chem, Downers Grove, IL) and CRP (#1010, Alpha Diagnostics International, Antonio, TX). Samples were measured in duplicate in each assay.