High blood cholesterol, hypercholesterolaemia
Hypercholesterolemia, also called high cholesterol, is the presence of high levels of cholesterol in the blood (Pic. 1). It is a form of high blood lipids (hyperlipidemia) and elevated levels of lipoproteins in the blood (hyperlipoproteinemia).
Most of the cholesterol is synthesized by the body and some have dietary origin. Cholesterol is more abundant in tissues which either synthesize more or have more abundant densely-packed membranes, for example, the liver, spinal cord, and brain. It plays a central role in many biochemical processes, such as the composition of cell membranes and the synthesis of steroid hormones.
There are several types of cholesterol found in the body:
Elevated levels of non-HDL cholesterol and LDL in the blood may be a consequence of diet, obesity, inherited (genetic) diseases (such as LDL receptor mutations in familial hypercholesterolemia), or the presence of other diseases such as diabetes and an underactive thyroid.
Familial hypercholesterolemia (FH) is a genetic disorder characterized by high cholesterol levels, specifically very high levels of low-density lipoprotein, in the blood and early cardiovascular disease (Pic. 2). Since individuals with FH underlying body biochemistry is slightly different, their high cholesterol levels are less responsive to the kinds of cholesterol control methods which are usually more effective in people without FH, such as dietary modification and statin tablets. Nevertheless, treatment (including higher statin doses) is usually effective.
There are often no symptoms or signs of high cholesterol – one can have high cholesterol and feel well. Therefore, it is important to have regular cholesterol checks by doctor. This is done by a simple blood test.
Avoiding trans fats and replacing saturated fats in adult diets with polyunsaturated fats are recommended dietary measures to reduce total blood cholesterol and LDL in adults. In people with very high cholesterol (e.g. familial hypercholesterolemia), diet is often not sufficient to achieve the desired lowering of LDL, and lipid-lowering medications are usually required. If necessary, other treatments such as LDL apheresis (a nonsurgical therapy that removes low-density lipoprotein (LDL) cholesterol from a patient’s blood) or even surgery (for particularly severe subtypes of familial hypercholesterolemia) are performed.
High blood cholesterol levels typically do not cause any signs or symptoms, but can increase the chances for heart disease.
Although hypercholesterolemia itself is asymptomatic, longstanding elevation of serum cholesterol can lead to atherosclerosis (hardening of arteries). Moreover, there is evidence that statins, drugs used to lower cholesterol, cause abnormalities in fetal development. A sudden blockage of a coronary artery may result in a heart attack. A blockage of an artery supplying the brain can cause a stroke.
Temporary ischemia (restriction in blood supply) of the brain (commonly referred to as a transient ischemic attack) may manifest as temporary loss of vision, dizziness and impairment of balance, difficulty speaking, weakness or numbness or tingling, usually on one side of the body. Insufficient blood supply to the heart may cause chest pain, and ischemia of the eye may manifest as transient visual loss in one eye. Insufficient blood supply to the legs may manifest as calf pain when walking, while in the intestines it may present as abdominal pain after eating a meal.
Some types of hypercholesterolemia lead to specific physical findings. For example, familial hypercholesterolemia may be associated with xanthelasma palpebrarum (yellowish patches underneath the skin around the eyelids; Pic. 3), arcus senilis (white or gray discoloration of the peripheral cornea), and xanthomata (deposition of yellowish cholesterol-rich material) of the tendons, especially of the fingers.
PCOS and high cholesterol go hand in hand. In a healthy individual, LDL’s or the “bad” cholesterol are usually very low and HDL’s, which are the healthy or “good” kind, are high. Unfortunately, because of this condition, the ratio of HDL’s to LDL’s is completely reversed.
Lifestyle changes recommended for those with high cholesterol include: smoking cessation, limiting alcohol consumption, increasing physical activity, and maintaining a healthy weight. Overweight or obese individuals can lower blood cholesterol by losing weight - on average a kilogram of weight loss can reduce LDL cholesterol by 0.8 mg/dl.
Eating a diet with a high proportion of vegetables, fruit, dietary fibre, and low in fats results in a modest decrease in total cholesterol.
Organized screening approaches for familial hypercholesterolemia (FH) can be “targeted” (selective) to individuals that meet pre-specified risk criteria (e.g., those who have a positive family history for early coronary heart disease) or “universal” screening that involves evaluating all individuals in a particular segment of a population (e.g., specific age groups) for parameters associated with FH (e.g., abnormally high cholesterol levels). In both cases, these approaches would then lead to more or less systematic and centrally-coordinated cascade testing approaches in which at-risk family members of index cases would be identified and assessed.
It isn’t entirely clear why cholesterol affects fertility but the waxy substance is key to the synthesis of sex hormones like oestrogen and testosterone in the body.
Lipids, especially cholesterol play significant role in the structural and functional activity of sperm. Excessive intake of high cholesterol or high fat diet may induce hypercholesterolemia/hyperlipidemia and disturb cholesterol homeostasis (stable internal environment) in the body which may adversely affect normal male reproductive functions. Additionally, high level of total cholesterol and low level of HDL cholesterol are important risk factors for erectile dysfunction (inability to obtain or sustain an erection). Feelings of stress, depression, guilt, or anxiety in infertile men can cause psychogenic impotence, which heightens the feelings of inadequacy that already accompany infertility. The psychological stress of infertility has been shown to affect sperm parameters in significant and demonstrable ways that may further contribute to difficulties with erectile potency; emotional reactions to the infertility may alter or even undermine a previous consolidation of a sense of self as sexually adequate.
A large number of human studies have also indicated an association between hypercholesterolemia and poor semen quality and subsequent male infertility. However, most of these studies have been conducted on normal infertile or obese men. Whether the hypercholesterolemia has any impact on sperm/seminal plasma cholesterol/lipid content is still poorly known.
The presence of high levels of LDL and low HDL is often associated with polycystic ovary syndrome (PCOS). PCOS reduces quality of life by depression, anxiety, obesity, infertility, and hirsutism (excessive body hair on parts of the body where hair is normally absent or minimal). PCOS is the most common cause of menstrual disturbance such as oligomenorrhea (infrequent menstruation), anovulation (ovaries do not release an egg during a cycle), menorrhagia (abnormally heavy and prolonged bleeding during menstruation), and infertility. Thus, natural conceiving is avoided.
High maternal cholesterol levels during pregnancy are now linked with increased risks of preterm delivery, gestational diabetes and preeclampsia (condition occurring after week 20 of pregnancy that may include high blood pressure and protein in the urine), as well as the later development of atherosclerosis in offspring.
Therefore, regulation of serum lipid profile may be useful to some extent, for proper reproductive functions and management of infertility.