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Q: " ... I take a tablet a day for my underactive thyroid gland, lead healthy life style, exercise regularly, pay attention to what I eat; smoke and drink bier or wine only occasionally. Recently I have been diagnosed to have high cholesterol levels. I am puzzled with the recent results, could you tell me what may have caused that?"

Dr. Keti:

Cholesterol and Underactive Thyroid:
If you are being treated for an underactive thyroid and are not taking enough thyroid hormone, some of the symptoms of hypothyroidism such as sluggishness, mental dullness, feeling cold, or muscle cramps may persist. In addition, you may have problems with elevation of cholesterol which could increase your risk for hardening of the arteries (arteriosclerosis). (1).
The decrease of thyroid hormone effect on metabolism causes an increase in total cholesterol, low-density lipoprotein cholesterol (LDL), and possible change in high-density lipoprotein cholesterol (HDL). In addition, medical conditions associated with hypothyroidism include anemia, dilutional hyponatremia, and hyperlipidemia.(5)

Causes of High Cholesterol in Blood:
a.In Western society, over-eating, especially of saturated fats, contributes to high blood cholesterol levels (over 5.2 mmol/L or 200 mg/dL) in most adults. Other important causes are:

  • Inherited defects in body chemistry. Usually more than one member of the family is affected and the cholesterol levels are high, over 280 mg/dL in adults.
  • Some drugs cause increase in blood cholesterol levels.
  • Thyroid, kidney,liver, diabetes, and other disorders may increase blood cholesterol. (2)

Age and Gender: As women and men get older, their cholesterol levels rise. Before the age of menopause, women have lower total cholesterol levels than men of the same age. After the age of menopause, women's so called "bad" cholesterol or Low-density lipoprotein (LDL) levels tend to rise. (3)The guidelines of the American Heart Association define hypercholesterolemia as a blood cholesterol concentration greater than or equal to 240 mg/dL. Desirable cholesterol concentrations are less than 200 mg/dL.

Diagnosis and Treatment Discussion:
It does not take much thyroxine to treat a hypothyroid patient, and very few patients require more than 150 micrograms daily. On the other hand, thyroid failure is an ongoing process. As a result, a dose that is appropriate for a patient one year may subsequently be too low. Therefore blood tests performed every year or two will guide adjustment of thyroxine.
The dose usually needs to be increased during pregnancy.
On the other hand, elderly patients require less thyroxine, so that the dose may need to be decreased as patient ages. Once the proper dosage of medication is achieved, the patient should feel completely well and be free of hypothyroid symptoms.

In cases when one takes too much thyroid hormone, symptoms mimicking an overactive thyroid, including nervousness, palpitations, insomnia, and tremor occur. In addition, thyroid hormone excess may also cause excessive calcium loss from bones, increasing the risk for osteoporosis and fractures in later years. resources(1)

For patients with heart conditions or diseases, an optimal thyroid dose is particularly important. Even a slight excess may increase the patient's risk for heart attack or worsen angina. Some physicians feel that more frequent dose checks and blood hormone levels are appropriate in these patients.
There are other potential problems with other drugs including iron-containing vitamins. All women and men taking iron supplements should discuss this with their physician.

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