Introduction
The thyroid gland, which is located in the neck, secretes hormones necessary
for growth and proper metabolism. The gland plays an important role in the
growth and mental development of both the fetus and child. It continues to
play a strong role in heart rate and weight during adulthood. Metabolic
disorders occur when the thyroid secretes too little or too much hormone. It
is interesting to note that diseases related to the thyroid are more common
in women than in men. This is probably because thyroid disease is often
autoimmune (antibody mediated) and most autoimmune conditions are more
common in women.
The double-lobed thyroid gland creates two forms of thyroid hormone:
thyroxine (T4) and triiodothyronine (T3). T4 is the more abundant hormone
produced though the body converts T4 into T3, a more potent hormone. In
general, thyroid hormones influence growth and metabolism.
Hyperthyroidism
Hyperthyroidism occurs approximately eight to ten times more often in women
than in men, with women in their twenties and thirties the most commonly
affected. This condition is the result of an excessive amount of thyroid
hormone in a person’s system.
There are a number of disorders associated with it. The most common form of
hyperthyroidism, Graves’ disease, is an autoimmune condition that results in
the overproduction of thyroid hormone by an enlarged thyroid gland. In
addition to the classic features of increased production of thyroid hormone
and a diffusely enlarged thyroid gland (goiter), some people with Graves’
disease may develop exophthalmos (prominent eyes that protrude from the
sockets) and edema (swelling) of the legs.
For people in their seventies and eighties, hyperthyroidism is often the
result of a thyroid with several nodules or lumps that make too much thyroid
hormone. This condition, called Plummer’s disease, is often accompanied by
apathy, depression, weight loss, and irregular heart-beats. It can also
accelerate osteoporosis.
The following is a list of signs and symptoms commonly associated with
hyperthyroidism:
Palpitations and rapid heart rate
Nervousness and anxiety
Enlarged thyroid gland
Weight loss or gain
Increased appetite
Frequent, loose bowel movements
Heat intolerance
Increased perspiration
Insomnia
Fatigue
Tremor
Brisk reflexes
Difficulty exercising
Shoulder and thigh weakness
Prominent eyes
Lower leg swelling
Nail changes
Gritty eyes
Hair loss
Oily skin
Inability to concentrate
Emotional changes
Increased libido
Menstrual irregularities
Diagnosis
The diagnosis of hyperthyroidism is confirmed by blood tests that show a
decreased thyroid stimulating hormone (TSH) level and elevated T4 and T3
levels. TSH is a hormone made by the pituitary gland in the brain that tells
the thyroid gland how much hormone to make. When there is too much thyroid
hormone, the TSH will be low. A radioactive iodine scan (a test that uses
injected radioactive iodine to examine the activity of the thyroid gland)
will show an enlarged thyroid gland that is over-functioning.
Treatments
Surgery is rarely necessary in the treatment of hyperthyroidism. Graves’
disease may be treated with radioactive iodine or antithyroid drugs, namely
propylthiouracil (PTU) and methimazole (tapazole).
Radioactive iodine treatment
One dose of radioactive iodine, taken by mouth, is usually sufficient to
cure Graves’ disease. It works by destroying the ability of thyroid cells to
make thyroid hormone. The iodine is predominantly excreted in the urine. I
advise my patients to urinate promptly after their treatment to minimize the
possibility of side-effects from the medication. Those who undergo
radioactive iodine treatment should not have prolonged contact with children
for appro ximately three days – because children are more sensitive to
radiation. I also advise patients who have recently undergone treatment to
flush the toilet twice, rinse the sink twice after brushing their teeth and
to use plastic silverware and paper plates. Alternatively, dishes and
utensils may be cleaned in a dishwasher. As daunting as it may sound, the
treatment of Graves’ disease with radioactive iodine has not been shown to
increase the risk of cancer.
However, many people who receive radioactive iodine do subsequently become
hypothyroid (described below) since the treatment destroys the ability of
the thyroid cells to produce thyroid hormone. Hypothyroidism may occur
months or even years after therapy. For people who have undergone this
treatment, it’s best to have thyroid function tests performed yearly at
least.
Radioactive iodine is not appropriate for pregnant women or those women who
plan to conceive in the near future. I instruct all my patients of
reproductive age not to become pregnant within nine months of treatment.
Radioactive iodine is also appropriate treatment for nodules in the elderly
that produce excessive amounts of thyroid hormone.
Antithyroid drugs
Unlike radioactive iodine treatment, which actually destroys thyroid tissue
and thus the ability to make hormone, antithyroid drugs are used to inhibit
thyroid hormone production. For this reason, they have only a 30 to 50%
chance of actually curing Graves’ disease. They are generally taken for
12-24 months. Hyperthyroidism can be well controlled by these medications,
but once the drugs are stopped, the disease may relapse. Propylthiouracil (PTU)
is taken two to four times per day and tapazole one or two times per day.
PTU additionally inhibits the conversion of T4 to T3.
A major adverse effect of antithyroid drugs is agranulocytosis, which is a
severe decrease in the white blood cells necessary to fight infections. This
condition can be life threatening for a person who gets sick with a
dangerously low granulocyte (white blood cell) count. I instruct my patients
to immediately stop their antithyroid medication if they get a fever, sore
throat or any other sign of infection and have a complete blood count
checked. If the white blood cell count is normal, they may resume their
antithyroid drugs. Agranulocytosis is usually reversible if the antithyroid
medication is stopped. Other side effects of these drugs include rashes,
hepatitis (liver inflammation), and joint aches.
After treatment
Hyperthyroid patients that they must be careful about the amount of food
they eat following treatment if they do not want to gain weight. With the
restoration of normal thyroid function, an increase in weight will accompany
a persistently exaggerated appetite.
Hypothyroidism in Pregnancy
Several symptoms are common to both pregnancy and hyperthyroidism. These
symptoms include: palpitations, anxiety, shortness of breath and fatigue.
Ideally, hyperthyroidism should be definitively treated prior to becoming
pregnant. If this is not possible, antithyroid drugs are the best treatment
option during pregnancy. Both PTU and methimazole are transferred from the
mother to the fetus through the umbilical cord, but PTU is the preferable
drug since it is less transferred. It has been suggested that an abnormality
of the fetal scalp may be associated with methimazole. I use the lowest
possible dose of PTU in my pregnant patients and try to stop treatment in
the third trimester if possible. Women who are pregnant and hyperthyroid
should be carefully monitored throughout their pregnancy. As well, because
the drug is in the mothers’ system, women who take antithyroid medication
should bottle-feed instead of nurse.
Hypothyroidism
Where hyperthyroid people make too much thyroid hormone, hypothyroid people
don’t make enough. Again, women develop hypothyroidism more frequently than
men, and it is most often diagnosed in people between the ages of thirty and
sixty. A common form of hypothyroidism results from the treatment of Graves’
disease with radioactive iodine. Hashimoto’s thyroiditis is the most common
non-drug induced form of hypothyroidism. In this condition, antibodies
(normally used to fight infections) are produced against the TSH receptor
which inhibits production of thyroid hormone.
Clinical features
The following is a list of signs and symptoms commonly associated with
hypothyroidism:
Fatigue
Weight gain
Constipation
Decreased pulse rate
Cold intolerance
Diminished reflexes
Goiter
Dry skin
Dry hair
Hair loss
Brittle nails
Depression
Decreased libido
Menstrual irregularities
Decreased fertility
Muscle aches
Swelling of the eyelids, hands and feet
Increased cholesterol
Diagnosis
The diagnosis of hypothyroidism is confirmed by blood tests that show an
increase in TSH and decreased levels of T4 and T3.
Treatments
There is no cure for hypothyroidism. Synthetic T4 (levothyroxine), an oral
medication taken daily, is the treatment of choice. When used appropriately,
this is a very safe medication.
Hypothyroidisim in Pregnancy
Levothyroxine may be taken during pregnancy and breast-feeding. During
pregnancy, the thyroid gland enlarges and thyroid hormone requirements may
increase. I carefully monitor all hypothyroid pregnant women and increase
their thyroid hormone doses as necessary. All babies born in American
hospitals are routinely screened for hypothyroidism.
Thyroiditis
Post-partum thyroiditis
Post-partum thyroiditis is an inflammation of the thyroid gland that occurs
following delivery, and it is estimated that this condition occurs in up to
20% of mothers. It often goes undiagnosed, as it is a painless condition and
it’s symptoms, such as nervousness, fatigue, weight loss and emotional
changes are often attributed to the natural post-partum state. If you
suspect you are experiencing a post-partum depression, you should have your
thyroid hormone blood levels checked. In post-partum thyroiditis, there is
an initial hyperthyroid phase that may last two to three months, which is
then followed by a hypothyroid phase of up to nine months. I often treat
women with T4 during the hypothyroid phase. In approximately 10% of women
with post-partum thyroiditis, the hypothyroidism is permanent; however the
majority fully recover.
Women with Hashimoto’s thyroiditis and Graves’ disease have an increased
incidence of post-partum thyroiditis, which may recur with subsequent
pregnancies.
Subacute thyroiditis
In contrast to post-partum thyroiditis, which is painless, subacute
thyroiditis is painful. It often occurs in conjunction with an upper
respiratory infection but does not resolve as rapidly as the infection.
Women are affected more frequently than men, most often between the ages of
thirty and fifty. A person with subacute thyroiditis may experience pain
radiating from the thyroid to the jaw or ear on either one or both sides of
his or her face. The thyroid gland may be exquisitely tender in the initial
phase, and the person may experience symptoms of hyperthyroidism (see
above). The initial hyperthyroid phase is followed by a hypothyroid phase,
which may require treatment with T4. Approximately 10% of those affected
become permanently hypothyroid. Aspirin and non-steroidal anti-inflammatory
drugs such as ibuprofen may suffice for the pain. In more severe cases,
steroids are useful. Subacute thyroiditis may recur.
Thyroid Nodules
Thyroid nodules, or ‘lumps’ on the thyroid, are also more common in women
than in men. The thyroid often functions normally in the setting of both
benign and malignant nodules. Multiple nodules within the same thyroid gland
are generally benign. If you have a single thyroid nodule, or one that is
clearly larger than the others, you should have a fine needle aspiration
biopsy performed, which involves retrieving cells from the nodule with a
thin needle so the cells can be studied. Benign (non-cancerous) thyroid
nodules may be followed by observation and suppressive treatment with T4.
Malignant (tending to spread) thyroid nodules should be surgically removed.
Thyroiditis Cancer
Papillary carcinoma
The most common form of thyroid cancer is papillary carcinoma. Women develop
this disease three times as often as men, and most people with papillary
carcinoma are diagnosed between the ages of thirty and fifty. When diagnosed
before age forty, papillary carcinoma is unlikely to be aggressive and may
not alter a person’s lifespan. Following thyroidectomy, thyroid hormone
replacement is taken by the patient. Radioactive iodine may be administered
in large doses to destroy any remaining thyroid tissue.
Follicular carcinoma
Follicular carcinoma, the second most common type of thyroid cancer, also
affects women three times more often than men. The average age of those who
are diagnosed with follicular carcinoma is sixty, and it tends to be more
aggressive than papillary carcinoma. Follicular carcinoma may metastasize
(spread) to the bones and lungs. Treatment includes surgical removal of the
thyroid, T4 replacement, radioactive iodine, and occasionally radiation and
chemotherapy if required.
Conclusion
Thyroid disease occurs with much greater frequency in women than in men.
Many different organ systems can be affected by the presence of abnormal
levels of thyroid hormone resulting in a whole host of symptoms. There are a
number of treatments available for diseases related to the thyroid. If you
suspect you may be experiencing symptoms similar to the ones listed above,
discuss them with your doctor.
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