Hypothyroidism or low thyroid hormone is a common condition in North America, particularly in Canada and the northern U.S. where levels of sunlight are low for much of the year, and soil mineral depletion is common. Low thyroid function affects approximately 20 to 25 percent of the female population and about 10 percent of males. An additional 30 percent of persons over the age of 35 may also have sub-clinical or mild hypothyroidism whereby their thyroid stimulating hormone (TSH) is within normal range, but they have many of the symptoms of low thyroid. The thyroid secretes two hormones – T3 and T4 – that are crucial for controlling our metabolism. Because thyroid hormones affect every cell in the body, a deficiency will result in many symptoms.
The thyroid is a small gland that lies below the Adam’s apple in the neck, wrapped around both sides of the trachea. It secretes thyroid hormones that control many metabolic functions in the body. Thyroid hormones stimulate the production of proteins and increase the use of oxygen by cells in the body. Iodine is required by the thyroid to produce thyroid hormones. A careful recycling process occurs in the thyroid to ensure adequate thyroid hormones are available to control the body’s metabolic rate. The following hormones and substances directly affect the thyroid or are released by it:
Thyrotropin-releasing hormone (TRH) is secreted by the hypothalamus, a brain centre that coordinates the actions of the nervous and endocrine systems. TRH triggers the pituitary to secrete TSH.
Thyroid stimulating hormone (TSH) is secreted by the pituitary in response to TRH. TSH stimulates the production of thyroid hormones and the growth of thyroid cells (excess TSH causes thyroid enlargement, or goiter).
Calcitonin is a thyroid hormone involved in the homeostasis of blood calcium levels. It lowers the amount of calcium and phosphate in the blood as needed, by inhibiting bone breakdown and accelerating the assimilation of calcium. Thus, the thyroid is involved in bone health and diseases such as osteoporosis.
Thyroxin (T4) is the most abundant thyroid hormone and is manufactured in the thyroid gland. It is synthesized from tyrosine and includes four molecules of iodine per molecule of thyroxin hormone.
Triiodothyronine (T3) is the most active thyroid hormone, with four to ten times the activity of T4. It includes three molecules of iodine molecule of triiodothyronine hormone. Twenty percent of T3 is produced and secreted by the thyroid gland and the other 80 percent is converted from T4 in the liver and other organs. Many factors contribute to the conversion of T4 to the more active T3, including liver health, low stress levels, the types of foods you consume and more.
At any given time, most T3 and T4 molecules in the body are bound tightly to blood proteins. Only a small amount of each circulates as a “free” hormone that is physiologically active. For example, unbound T4 accounts for approximately 0.05 percent of total T4. Unbound hormone levels are seldom measured by medical doctors, yet these levels are most accurate for determining thyroid function.
A delicate balance must be maintained to keep a steady metabolic rate in the body. The hypothalamus and pituitary glands work in concert with the proteins of the body, T4, the liver and other organs to maintain that balance.
When the thyroid produces too much thyroid hormone, hyperthyroidism develops. Autoimmune reactions against the thyroid can cause hyper-thyroidism; Graves’ disease is one such condition. The immune system malfunctions, causing an increase in thyroid hormone. Goiter, a greatly enlarged thyroid gland, is seen in those with Graves’ disease and is due to the excessive secretion of thyroid hormone. Thyroiditis, an inflammation of the thyroid gland, can initially cause hyperthyroidism, but eventually the damage to the thyroid caused by the inflammation causes hypothyroidism or low thyroid function.
Low Thyroid Function, Peri-menopause, Menopause and Weight Gain: Estrogen decides body fat distribution, and, in women, fat is stored on the hips, bottom, abdomen and thighs. Fat cells manufacture and store estrogen. Some researchers believe women get an increase in body fat around menopause to ensure adequate estrogen from fat cells. Others believe that it is low thyroid and exhausted adrenals that promote mid-section fat gain. Considering that excess fat reduces our life expectancy, I tend to believe the latter because the body is generally programmed to ensure our survival.
I mentioned earlier that as many as 30 percent of people over the age of 35 could be walking around with sub-clinical low thyroid function. We know that low thyroid function promotes many hormonal problems that could be remedied with thyroid-supporting nutrients or medication (thyroid hormones).
During the peri-menopausal years (the 10 to 15 years before menopause) and during menopause (menopause means one year with no periods), it is common for women to suffer a multitude of hormonal complaints. Hot flashes, night sweats and sleep disturbances are common complaints during this time in a woman’s life. Most think these symptoms are associated with a decline in estrogen, but they are also hallmark symptoms of low thyroid, especially night sweats and insomnia. Most menopausal women are given hormone replacement therapy with estrogen for these symptoms. Peri-menopausal women may be put on the birth control pill. The problem with these treatments is that estrogen further shuts down the thyroid: high estrogen levels interfere with the thyroid hormones, particularly the utilization of T3, the most biologically active thyroid hormone. I have to reiterate that too much estrogen, either from hormone replacement therapy, your own estrogen, or the environment, causes a host of problems and also impairs thyroid function.
Many women experience a 10- to 15-pound weight gain and increased blood pressure when they start taking synthetic estrogen at menopause. This happens because estrogen is an antagonist to thyroid hormone, and the metabolic rate slows down. As this happens, many women develop difficulties with fat metabolism, because one of the functions of the thyroid hormones is to stimulate fat cells to burn fat. Weight control problems result.
In addition, serum cholesterol or triglyceride levels may increase. Thyroid activity can also be inhibited by high levels of androgens (male sex hormones) circulating in the blood. Depression and fatigue are the most common thyroid symptoms in menopausal women.
Many people suffer with mild or sub-clinical low thyroid function – their thyroid stimulating hormone (TSH, the hormone that stimulates your thyroid to make thyroid hormones) is greater than 2.0 IU/ml but less than the 5.5 IU/ml level indicative of hypothyroidism. As such, they contend with the many symptoms of low thyroid function but are not being treated for it. If you are trying to lose weight and have followed a healthy eating plan and exercised and still cannot lose a pound, you may have sub-clinical low thyroid function.
Many people’s TSH falls within the conventional parameters for normal (0.5 to 5.5), but most people with levels greater than 2.0 to 3.0 have symptoms of low thyroid function. Enlightened doctors refer to such people as having sub-clinical, or functional, low thyroid function.
If a diagnosis of low thyroid is based solely on a TSH reading, without taking other symptoms into account, it may take 10 years before thyroid hormone levels drop low enough to trigger a mainstream diagnosis of low thyroid function. In the meantime, the person with low thyroid function symptoms will go through much unnecessary suffering. Make sure you go for your thyroid test first thing in the morning for more accurate results.
Low Thyroid Function and Hormonal Problems: It is common for the thyroid to be functionally, or even clinically, out of balance in women who experience hormone-related problems such as premenstrual syndrome (PMS), infertility, ovarian cysts, fibroids, endometriosis, fibrocystic breasts, dysmenorrhea (menstrual pain), metrorrhagia (heavy bleeding) or menopausal symptoms. Back in the days before fertility drugs, when a woman could not get pregnant or had recurring miscarriages, doctors prescribed thyroid hormone with some success. Women who suffer post-partum depression could also benefit from thyroid hormone as childbearing can often exhaust the adrenals and promote low thyroid.