5: 30-year-old woman with palpitations Flashcards
Signs and Symptoms of Hyperthyroidism
Hyperthyroidism presents with multiple symptoms that vary according to the age of the patient, the duration of the illness, the magnitude of hormone excess, and presence of comorbid conditions. Symptoms are related to the thyroid hormone’s stimulation of catabolism, and enhancement of sensitivity to catecholamines.
In patients under the age of 50, the most common signs and symptoms of hyperthyroidism are:
- Heat intolerance (92%)
- Tachycardia (96%) due to increased adrenergic tone and heightened conduction
- Fatigue (84%)
- Weight loss (50%) due to increased calorigenesis and gut motility causing hyperdefecation and malabsorption.
- Tremor (84%)
- Increased sweating (96%)
- Exertional dyspnea caused by O2 consumption, CO2 production, and respiratory muscle weakness
Depression and hyperreflexia are less common but can be present.
Diarrhea and light periods can also occur with hyperthyroidism.
Many of the typical symptoms of hyperthyroidism are absent in patients older than age 70.
Patients who are older than 70 may present with sinus tachycardia (71%) and/or fatigue (56%), but they can also present with atrial fibrillation or weight loss, and no other symptoms.
Causes of Enlarged Thyroid (Goiter)
Lack of iodine
Worldwide, the lack of iodine is the most common cause of goiter. In fact, iodine deficiency is the most common, yet easily preventable cause of developmental delay and mental retardation in the world. Areas that are the most affected are in northern Africa and Pakistan. Iodized salt is the easiest and least expensive way to supplement iodine.
Hypothyroidism
Hashimoto disease, which causes hypothyroidism, is a common cause of goiter.
Hyperthyroidism
Graves disease, which causes hyperthyroidism, also causes goiter. In fact, an enlarged thyroid can be seen in patients with too much, normal amounts or not enough thyroid hormone.
Nodules
Nodules, either single or multiple, can also cause an enlarged thyroid.
Thyroid cancer
Thyroid cancer is usually detected by palpating an enlarged, nodular thyroid.
Pregnancy
Pregnancy can occasionally cause a slight enlargement in the thyroid.
Thyroiditis
Thyroiditis can also cause an enlarged, often tender, thyroid gland.
Hypothalamic-Pituitary Axis
The hypothalamus releases thyrotropin releasing hormone (TRH) which stimulates the pituitary to produce and release thyroid stimulating hormone (TSH). TSH stimulates the thyroid to make thyroid hormone (T3 and T4).
–When thyroid hormone levels are high: The presence of excess thyroid hormone exerts negative feedback on the hypothalamus and anterior pituitary, and suppresses the release of both TRH from hypothalamus and TSH from anterior pituitary gland.
–When thyroid hormone levels are low: The hypothalamus releases TRH. TRH stimulates the pituitary to produce TSH. The TSH, in turn, stimulates the thyroid to produce thyroid hormone until levels in the blood return to normal.
Therefore, if there are elevated levels of circulating thyroid hormones , suppression of the pituitary gland via a negative feedback loop will result in a low TSH.
Conversely, when there are decreased levels of circulating thyroid hormones , the absence of suppression of the pituitary will result in an increased TSH.
If a primary pituitary problem interferes with the feedback cycle - for example, if a pituitary adenoma develops that is not suppressed by excess thyroid hormone - then TSH may not accurately reflect the levels of circulating thyroid hormone, and drawing a T4 level helps in the investigation.
Graves Disease
- -Autoimmune disease in which thyrotropin receptor antibodies (also called thyroid stimulating immunoglobulins) are produced. These antibodies stimulate the thyroid gland to enlarge and to produce more thyroid hormone.
- -Causes about 60% to 80% of hyperthyroidism.
- -Women are five to 10 times more likely than men to get it.
- -Peak incidence is between ages 40 and 60.
- -Often occurs with family history of thyroid disease; can also be associated with other autoimmune diseases.
- -Triggers include stressful life events, high iodine intake, or a recent pregnancy.
Eye Involvement in Graves Disease
The most common manifestations of Graves ophthalmopathy (eye problems) are eyelid retraction and exophthalmos.
Primary symptoms of the eye manifestations of Graves disease are related to corneal irritation from eyelid retraction.
While most of the time the eye signs and symptoms are bilateral, they can be unilateral.
While 50% of patients with Graves have some eye involvement by MRI, only about 20% to 30% of those are clinically relevant. In up to 10% the eye manifestations can happen when the patient is euthyroid or even hypothyroid. Treatment of hyperthyroidism does not affect the eye manifestations. In fact, some patients who get radioactive iodine will experience worsening symptomatology.
Common Symptoms of Hypothyroidism
Weight gain, cold intolerance, pedal edema, heavy periods, and fatigue all arise from slowed metabolism. Fatigue is common to both hyper- and hypothyroidism.
Treatment of Graves Disease
Medication to suppress thyroid hormone production:
- Methimazole is the most commonly used medication to suppress thyroid hormone production.
- -Side effects are rare, but less than 1% of people who take methimazole have a serious side effect known as agranulocytosis in which the bone marrow stops producing white blood cells. This leaves patients vulnerable to serious infections.
- -It takes up to three months to suppress thyroid production , although patients usually start to notice improvement in their symptoms after one month.
- -Patients typically need to stay on medications for several years . More than half of patients return to hyperthyroidism if they try stopping medications.
- -The appropriate dose of medication fluctuates over time and people on medication need to come in for blood work often for adjustments. People on medication are more likely to have symptoms because fluctuations are hard to predict. - Oral dose of radioactive iodine:
- -Alternative to thyroid hormone suppressant medication. More commonly used in the United States.
- -Iodine concentrated in the thyroid and has very few side effects .
- -During the course of a few months the iodine destroys most of the overactive thyroid cells and the level of thyroid hormone falls and the thyroid gland shrinks in size.
- -Eventually most people who have this treatment start having too little thyroid in their bloodstream so that they need to start taking small doses of thyroid hormone to replace it.
- -Low thyroid is relatively easy to manage once you have found a dose where the patient feels normal and the TSH is in the normal range. Blood levels usually need to be drawn once or twice yearly and the dose of thyroid replacement usually stays about the same.
Radioactive Iodine Treatment and Follow-Up
Radioactive Iodine Treatment
- –Obtain a pregnancy test before initiating radioactive iodine treatment.
- –Advise patients that they should not be near pregnant women or young children for several days following radioactive iodine treatment because the radioactive iodine is excreted in urine and stool. Fetuses or young children exposed to this could have deleterious effects on their thyroid.
- –Side effects include transient soreness of the neck or brief worsening of symptoms but they should resolve within a few days. Furthermore, people with ophthalmopathy can have worsening of eye symptoms.
Follow-up for Radioactive Iodine Treatment
—The patient needs to be seen within a few months after her radioactive iodine treatment to see when to discontinue propranolol (if prescribed) and to follow her TSH. The patient should have her TSH drawn every two to three months until it has stabilized. The time frame can be extended after that to six months or longer. Since she will become hypothyroid at some point, it is important to alert the patient to symptoms of hypothyroidism she could expect, so she can be tested earlier if need be.
Thyroid Replacement Therapy
> > A typical starting dose of thyroxine in primary hypothyroidism (such as that which occurs following radioactive iodine treatment) is 1.5 to 1.8 mcg per kilogram.
> > Increasing the dose slowly is important, especially in elderly patients and in patients like Ms. Waters who are mildly hypothyroid. TSH should be repeated in six weeks.
> > When a stable TSH level has been achieved in primary hypothyroidism, TSH can be checked once or twice annually.
> > Some people who have radioactive iodine treatment still have enough thyroid left to relapse. Occasionally they need a second treatment.
T4 Level for Primary Pituitary Pathology
While the thyroid stimulating hormone (TSH) is usually sufficient to make a diagnosis of both hyperthyroid and hypothyroid, there are some unusual causes of low TSH due to primary pituitary pathology. In those cases the TSH does not reflect the circulating thyroid level. In those cases, T4 level is low because the pituitary is not stimulating the gland to make thyroxine.
Studies to Determine the Etiology of Hyperthyroidism
Radioactive iodine uptake (RAIU) test and scan measures the amount and pattern of radioactive iodine taken up by the thyroid in the 24 hours following ingestion of a set dose. Normal RAIU uptake is 15% to 30% of the ingested dose.
The various etiologies of hyperthyroidism can be differentiated as conditions that manifest as high RAIU (>30%) or low RAIU (<15%).
For example, excess circulating thyroid hormone which occurs in Graves disease as a result of increased creation of thyroid hormone results in increased radioactive iodine uptake used to synthesize the thyroid hormone.
Conversely, excess circulating thyroid hormone in subacute thyroiditis occurs as a result of the gland leaking excess hormone, so radioactive iodine uptake is low in this case, as more thyroid hormone is not synthesized.
Nodules
Nodules that cause hyperthyroidism are hyperfunctioning and caused increased radioactive iodine uptake.
“Cold” (non-thyroxine producing) nodules can be caused by cancer although typically in that case hyperthyroidism is not present.
Diffuse increased uptake suggests Graves disease whereas a nodular pattern indicates a single nodule or multi nodular disease.
Anti-thyrotropin releasing antibodies (TRAb)
are the pathologic mechanism for Graves disease and can be detected in the vast majority of patients with this condition. In patients with undiagnosed causes of hyperthyroidism, third-generation assays for TRAb are 97% sensitive and 99% specific for Graves. These antibodies are to be distinguished from anti-thryroid peroxidase (TPO) antibodies, which are elevated in 90% of patients with Hashimoto thryroiditis and 75% of patients with Graves.
Studies not used to determine the etiology of hyperthyroidism:
A thyroid ultrasound is used in the evaluation of thyroid nodules and thyroid enlargement but not hyperthyroidism. Ultrasound characteristics of a nodule can be used to stratify risk of malignancy and ultrasound can guide the fine needle aspiration of nodules that are not easily palpated. Ultrasound is starting to be used to differentiate Graves disease from other causes of hyperthyroidism when RAI scanning is not available or is contraindicated. Some experts predict that color-flow Doppler ultrasound may replace RAI scanning since it has similar accuracy but is safer, less costly and easier to administer.
An MRI of the thyroid gland is not necessary to diagnose hyperthyroid disease.
The following conditions can cause palpitations:
- -Cardiovascular: Arrhythmia, cardiomyopathy, hypovolemia
- -Psychiatric: Anxiety, panic attacks
- -Medications: Caffeine, stimulants, theophylline, and albuterol use
- -Substances: Tobacco, caffeine, alcohol intoxication or withdrawal, cocaine
- -Endocrinologic: Hyperthyroidism, pheochromocytoma, hypoglycemia
- -Hematologic: Anemia
- -Infectious: Febrile illness
