Hypocholesterolemia
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2008-05-28T21:59:25Z
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'''Hypocholesterolemia''' is the presence of abnormally low (''hypo-'') levels of [[cholesterol]] in the [[blood]] (''-emia''). While [[hypercholesterolemia]], the presence of ''high'' cholesterol, has been linked strongly with [[cardiovascular disease]], it is much less certain whether low cholesterol levels are intrinsically harmful.
==Classification==
According to most authorities, only total cholesterol levels below 160 mg/dL or 4.1 mmol/l are to be classified as "hypocholesterolemia"<ref name=Criqui>Criqui MH. (1994). Very Low Cholesterol and Cholesterol Lowering. Leaflet 71-0059. American Heart Association.</ref>.
==Causes==
Possible causes of low cholesterol are:{{Fact|date=November 2007}}
*[[hyperthyroidism]], or an overactive thyroid gland
*[[liver disease]]
*[[malabsorption]] (inadequate absorption of nutrients from the [[intestines]])
*[[malnutrition]]
*[[celiac disease]]
*[[abetalipoproteinemia]] - a rare genetic disease that causes cholesterol readings below 50mg/dl. It is found mostly in [[Jewish]] populations.
*[[hypobetalipoproteinemia]] - a genetic disease that causes cholesterol readings below 50mg/dl
*[[Manganese deficiency (medicine)|manganese deficiency]]
*[[Smith-Lemli-Opitz syndrome]]
*[[leukemia]]s and other hematological diseases<ref name="pmid2496554">{{cite journal |author=Marini A, Carulli G, Azzarà A, Grassi B, Ambrogi F |title=Serum cholesterol and triglycerides in hematological malignancies |journal=Acta Haematol. |volume=81 |issue=2 |pages=75–9 |year=1989 |pmid=2496554 |doi=}}</ref>
==Role in disease==
With the increased use of medication to suppress cholesterol, some have expressed concern that lowering cholesterol levels excessively will itself cause disease.
===Specific disease entities===
Demographic studies suggest that cholesterol levels form an U-shape curve when plotted against mortality; this suggests that low cholesterol is associated with increased mortality, mainly due to [[clinical depression|depression]], [[cancer]], [[cerebral hemorrhage|hemorrhagic stroke]] and respiratory diseases.<ref name=Jacobs>{{cite journal |author=Jacobs D, Blackburn H, Higgins M, ''et al'' |title=Report of the Conference on Low Blood Cholesterol: Mortality Associations |journal=Circulation |volume=86 |issue=3 |pages=1046–60 |year=1992 |pmid=1355411 |doi=}}</ref> It is possible that whatever causes the low cholesterol level also causes mortality, and that the low cholesterol is simply a marker of poor health.<ref name=Criqui/>
Links with depression have been supported by studies.<ref>{{cite journal |author=Suarez EC |title=Relations of trait depression and anxiety to low lipid and lipoprotein concentrations in healthy young adult women |journal=Psychosom Med |volume=61 |issue=3 |pages=273–9 |year=1999 |pmid=10367605 |url=http://www.psychosomaticmedicine.org/cgi/content/full/61/3/273}}</ref> In contrast, no evidence was found for a link with hemorrhagic stroke (although higher cholesterol levels conferred a relative protection), and neither did statin drugs worsen the risk.<ref>{{cite journal |author=Woo D, Kissela BM, Khoury JC, ''et al'' |title=Hypercholesterolemia, HMG-CoA reductase inhibitors, and risk of intracerebral hemorrhage: a case-control study |journal=Stroke |volume=35 |issue=6 |pages=1360–4 |year=2004 |pmid=15087556 |doi=10.1161/01.STR.0000127786.16612.A4 |url=http://stroke.ahajournals.org/cgi/content/full/35/6/1360}}</ref>.
The [[Heart Protection Study]] found no increase in either respiratory disease or neuropsychiatric illness in a large trial population taking a statin drug.<ref>{{cite journal |author= |title=MRC/BHF Heart Protection Study of cholesterol lowering with simvastatin in 20,536 high-risk individuals: a randomised placebo-controlled trial |journal=Lancet |volume=360 |issue=9326 |pages=7–22 |year=2002 |pmid=12114036|doi=10.1016/S0140-6736(02)09327-3}}</ref>
===Elderly===
In the elderly, low cholesterol may confer a health risk that may not be offset by the beneficial effects of cholesterol lowering.<ref>{{cite journal |author=Schatz IJ, Masaki K, Yano K, Chen R, Rodriguez BL, Curb JD |title=Cholesterol and all-cause mortality in elderly people from the Honolulu Heart Program: a cohort study |journal=Lancet |volume=358 |issue=9279 |pages=351–5 |year=2001 |pmid=11502313 |doi=10.1016/S0140-6736(01)05553-2}}</ref> Similarly, for elderly patients admitted to hospital, low cholesterol may predict short-term mortality.<ref>{{cite journal |author=Onder G, Landi F, Volpato S, ''et al'' |title=Serum cholesterol levels and in-hospital mortality in the elderly |journal=Am. J. Med. |volume=115 |issue=4 |pages=265–71 |year=2003 |pmid=12967690 |doi=10.1016/S0002-9343(03)00354-1}}</ref>
===Critical illness===
In the setting of critical illness, low cholesterol levels are predictive of clinical deterioration, and are correlated with altered [[cytokine]] levels.<ref>{{cite journal |author=Gordon BR, Parker TS, Levine DM, ''et al'' |title=Relationship of hypolipidemia to cytokine concentrations and outcomes in critically ill surgical patients |journal=Crit. Care Med. |volume=29 |issue=8 |pages=1563–8 |year=2001 |pmid=11505128 |doi=10.1097/00003246-200108000-00011}}</ref>
==References==
<references/>
[[Category:Lipid disorders]]
[[pt:Hipocolesterolemia]]