Reduced Cortisol

reduced cortisol maintains stress response (and prevents switch to parasympathetic system)

Studies finding lower cortisol in ME/CFS throughout the 24 hour cycle: <a class="externalLink" href="https://www.ncbi.nlm.nih.gov/pubmed/15922454" target="blank" rel="nofollow">one</a>, <a class="externalLink" href="https://www.ncbi.nlm.nih.gov/pubmed/9476760" target="blank" rel="nofollow">two</a>, <a class="externalLink" href="https://www.ncbi.nlm.nih.gov/pubmed/25260861" target="blank" rel="nofollow">three</a>, <a class="externalLink" href="https://www.ncbi.nlm.nih.gov/pubmed/15142269/" target="blank" rel="nofollow">four</a>, <a class="externalLink" href="https://www.ncbi.nlm.nih.gov/pubmed/11282703" target="blank" rel="nofollow">five</a>, <a class="externalLink" href="https://www.ncbi.nlm.nih.gov/pubmed/16439267" target="blank" rel="nofollow">six</a>.
Studies finding lower cortisol morning awakening response in ME/CFS: <a class="externalLink" href="https://www.ncbi.nlm.nih.gov/pubmed/14754825" target="blank" rel="nofollow">one</a>, <a class="externalLink" href="https://www.ncbi.nlm.nih.gov/pubmed/18160468" target="blank" rel="nofollow">two</a> (this study found only women had a lowered levels), <a class="externalLink" href="https://www.ncbi.nlm.nih.gov/pubmed/18378875" target="_blank" rel="nofollow">three</a> (this study found lowered levels in the morning, but increased levels in the evening).

From: <a id="null" class="null" href="https://academic.oup.com/edrv/article/24/2/236/2424377">https://academic.oup.com/edrv/article/24/2/236/2424377</a>

Reviewing the literature, there is a wealth of studies that have reported an assessment of basal function of the HPA axis. At the most basic, these studies report single baseline measures of plasma cortisol, either as the primary focus of the study or as part of a subsequent dynamic test (<a class="link link-ref link-reveal xref-bibr" data-open="R16">16</a>, <a class="link link-ref link-reveal xref-bibr" data-open="R17">17</a>, <a class="link link-ref link-reveal xref-bibr" data-open="R18">18</a>, <a class="link link-ref link-reveal xref-bibr" data-open="R19">19</a>, <a class="link link-ref link-reveal xref-bibr" data-open="R20">20</a>, <a class="link link-ref link-reveal xref-bibr" data-open="R21">21</a>, <a class="link link-ref link-reveal xref-bibr" data-open="R22">22</a>, <a class="link link-ref link-reveal xref-bibr" data-open="R23">23</a>, <a class="link link-ref link-reveal xref-bibr" data-open="R24">24</a>, <a class="link link-ref link-reveal xref-bibr" data-open="R25">25</a>, <a class="link link-ref link-reveal xref-bibr" data-open="R26">26</a>, <a class="link link-ref link-reveal xref-bibr" data-open="R27">27</a>, <a class="link link-ref link-reveal xref-bibr" data-open="R28">28</a>, <a class="link link-ref link-reveal xref-bibr" data-open="R29">29</a>, <a class="link link-ref link-reveal xref-bibr" data-open="R30">30</a>, <a class="link link-ref link-reveal xref-bibr" data-open="R31">31</a>, <a class="link link-ref link-reveal xref-bibr" data-open="R32">32</a>). Although a minority of these studies has reported lowered cortisol levels, usually in the morning, it is clear that such assessments are of very limited value: not only do they fail to allow for the stress of hospital attendance or cannulation/venepuncture, they are also inadequate in evaluating the function of a pulsatile hormone such as cortisol. This review will therefore focus on those studies that have undertaken serial measures of unstimulated cortisol and/or ACTH levels in blood or saliva and studies of 24-h urinary collections.