Hypothyroidism, also known as an underactive thyroid, is a condition in which the thyroid (that's the butterfly-shaped gland located at the front of your neck) doesn't generate enough of its vital hormones to meet the body's needs. Hypothyroidism occurs in about 5 out of every 100 Americans over the age of 12, although many cases aren't diagnosed because the symptoms are so mild. There are many factors that increase the likelihood of developing hypothyroidism, including being female and having a family history of the condition. In this article, we'll look at the genetics of hypothyroidism, how it's diagnosed and treated, and how you can be vigilant about your thyroid health. (Source, Source)
What Is Hypothyroidism?
First, a little thyroid 101. The thyroid is part of your body’s endocrine system, which uses hormones to control things like metabolism, reproduction, energy, and your response to injury and stress. The pituitary gland, a pea-sized organ that's located at the base of your brain, produces a hormone called TSH. TSH prompts your thyroid to secrete triiodothyronine (T3), and tetraiodothyronine (thyroxine or T4), two other hormones that control your metabolism, in addition to other important functions. (Source, Source)
If you have hypothyroidism, it means there aren't enough hormones making their way into your body and regulating things like your body temperature, your period, how you bounce back from injuries, and how your food digests and processes. According to the Mayo Clinic, symptoms of hypothyroidism can include:
- increased sensitivity to cold
- dry skin
- weight gain
- puffy face
- muscle weakness, aches, tenderness, and stiffness
- pain, stiffness, or swelling in your joints
- heavier than normal or irregular menstrual periods
- thinning hair
Diagnosis and Treatment of Hypothyroidism
If your health care provider suspects your thyroid isn't functioning normally, they will take blood to assess your levels of TSH, the hormone that lets your thyroid know how much T3 and T4 to make. If you're making too much TSH, that's an indication of hypothyroidism. Why? Because the pituitary is releasing increased amounts of TSH to stimulate the thyroid to produce more of its hormones. Elevated TSH suggests the thyroid is not responding. (Source)
There are actually two types of hypothyroidism:
- overt hypothyroidism, when your TSH levels are high and your levels of T4 are low, and
- subclinical hypothyroidism, when your TSH is high, but the rest of your thyroid hormones are fine.
Overt hypothyroidism needs to be treated immediately, but the jury is still out in some corners of the medical community as to whether everyone with subclinical hypothyroidism needs treatment. (Source, Source)
When hypothyroidism is left untreated, in time it may result in fertility challenges, heart issues, and birth defects. While there’s no cure for hypothyroidism, it may be treated with daily doses of synthetic thyroid hormone, which is monitored and adjusted by a health care provider.
Symptoms of hypothyroidism tend to start out mild and intensify over time, so it's possible you wouldn't notice them right away. In fact, according to the American Thyroid Association, there's no single set of symptoms that always occurs in people who have hypothyroidism, and it's important to be aware that many of the symptoms listed above also occur in people who have other medical conditions. (Source)
Risk Factors for Hypothyroidism
As we mentioned up top, women are 5 to 8 times more likely to develop hypothyroidism. (Source)
Additional risk factors include:
- a previous thyroid problem (like a goiter, an enlarged thyroid that causes visible swelling in the neck)
- surgery or radioactive iodine to address a thyroid problem
- radiation treatment on the thyroid, neck, or chest
- pregnancy within the previous 6 months
- other health problems such as Turner syndrome, celiac disease, diabetes, lupus, or rheumatoid arthritis
- family history of thyroid disease
It’s important to share with your health care provider as much as you know about your family’s medical history — especially when it comes to thyroid issues — because in some cases there may be a genetic connection.
Genetics and Hypothyroidism
Many studies suggest an individual’s thyroid hormone and TSH levels are determined genetically. Additionally, a study published in Clinical Endocrinology found that first degree relatives (parents, siblings, children) of patients with hypothyroidism due to Hashimoto’s disease — a common cause of autoimmune thyroid dysfunction — have an overall 9-fold higher risk of developing it as well. In the same study, women were more likely than men to have thyroid antibodies (indicating attack by their immune system) and hypothyroidism due to Hashimoto’s thyroiditis. (Source, Source)
What Is Congenital Hypothyroidism?
Congenital hypothyroidism, or hypothyroidism that’s present at birth, occurs in 1 in 3,000 to 4,000 live births, making it the most common congenital disorder of the endocrine system. It occurs when the thyroid is too small, develops in the wrong place, is absent altogether, or just doesn’t make enough thyroid hormones. (Source, Source)
Most of the time, congenital hypothyroidism just happens; there’s no other known instance of it in the family. It can be inherited, however, usually due to an autosomal recessive inheritance pattern. In this pattern, one mutated gene is inherited from each parent, whose health is rarely impacted by the condition they're passing on. (Source, Source.)
Congenital hypothyroidism isn't always permanent; up to 40% of cases are due to environmental causes (such as iodine deficiency in the mother) that resolve in the first few months of the baby’s life. (Source)
Hashimoto’s Disease and Hypothyroidism
Hashimoto’s is an autoimmune condition in which the immune system attacks the thyroid. While Hashimoto's and hypothyroidism aren't the same thing, inflammation caused by Hashimoto’s, also known as chronic lymphocytic thyroiditis, or Hashimoto’s thyroiditis, is the most common cause of hypothyroidism. The symptoms of Hashimoto’s include those of hypothyroidism, and you may also observe swelling at the front of your throat. And as with hypothyroidism, the progress of Hashimoto’s is slow, so you may not notice your thyroid levels dropping over time.
What Causes Hashimoto’s Disease?
It’s thought that Hashimoto’s is caused by a combination of environmental factors (radiation exposure, excessive iodine) and genetics. A group of genes known as human leukocyte antigens (HLA) may also be responsible for Hashimoto’s. These genes help the immune system distinguish proteins made by the body from proteins made by viruses and other agents, like bacteria. (Source, Source, Source)
According to a 2008 paper in the Journal of Autoimmunity, a specific type of HLA gene known as HLA-DR plays a big role in the development of Graves’ disease, an autoimmune disease in which too much thyroid hormone is generated. The jury is still out, though, as to whether HLA-DR plays a part in developing Hashimoto’s. (Source)
How Is Hashimoto’s Treated?
How Hashimoto’s is treated depends on how your thyroid is functioning. If your thyroid is normal, its function will be monitored, but no treatment will be given. When treatment is necessary, it comes in the form of levothyroxine, a synthetic thyroid hormone. Hashimoto’s can’t be reversed, but it may be possible to reduce symptoms through diet, keeping stress levels in check, and taking vitamins and probiotics. (Source)
Staying on Top of Your Thyroid Health
While several genes have been uncovered that seem associated with autoimmune thyroid diseases, genetics still accounts for just some occurrences. More research is needed to identify other causes.
There’s no sure-fire way to prevent hypothyroidism, and there’s also no documented evidence that eating certain foods, or staying away from them, will reverse it. According to the Mayo Clinic, having an adequate amount of iodine in your diet is essential for normal thyroid function. If you're eating a balanced diet, though, it’s unlikely you need an iodine supplement. Excessive intake of iodine can lead to hyperthyroidism, or an overactive thyroid gland, so talk to your health care provider before starting any supplementation. (Source)
If you've been diagnosed with hypothyroidism, you can prevent your symptoms from becoming serious. Consider your risk factors, and if you do have a history of thyroid problems in your family, make sure your health care provider knows. Report anything about your health that's not normal for you — an early diagnosis can make the path to feeling better a lot smoother.