Hypothyroidism

Hypothyroidism is a condition where the thyroid gland does not produce or secrete enough T3 and T4 hormones. It has several possible causes. Since every cell in a human body has receptors for thyroid hormones the effects of hypothyroidism are widespresad but in general will result in a slowing down of bodily functions.

Eitology and Pathology
Thyrotropin releasing hormone is produced in the hypothalamus and stimulates the pituitary to release thyroid stimulating hormone (TSH) which in turn stimulates the thyroid gland to create and release thyroxine (T4) and triiodothyronine (T3). T3 is much more biologically active than T4 and is responsible for most of the biological effects fo thyroid function. In addition to being made in the thyroid gland excess T4 is converted to T3 inside cells on an as needed basis.

Hypothyroidism is five times more likely to affect women than men. Average age at onset is between 30-60 yo but it can occur at any age.

Hypothyroidism can be primary, secondary or tertiary in nature. Which one it is classified as depends on the cause.

In primary hypothyroidism the thyroid gland itself is failing. This can be caused by thyroid specific disorders such as Graves or Hashimoto's, both of which are autoimmune disorders. It can also be the result of surgery or RAIU therapy to correct hyperthyroidism. LIthium and amniodarone (Cordarone) and lithium can also cause a decrease in thyroid function.

Secondary hypothyroidism is due to a malfunction in the pituitary gland which causes a drop in thyroid stimulating hormone (TSH), tumors, head trauma and infection are possle causes.

Tertiary hypothroidism is a malfunction in the hypothalmus which creates and secretes thyrotropin releasing hormone (TRH) which in turn controls pituitary release of TSH. Possible causes are the same as for pituitary malfunction.

Globally hypothyroidism is caused by mainly by inadequate intake of iodine. In the US salt is fortified with iodine so this is less of a problem and other primary causes listed above are more likely to cause hypothyroidism.

Cretanism is a term used to describe hypothyroidis if it develops in utero or neonatally. Newborns are tested for this at birth.

Signs and Symptoms
Thyroid hormone exerts a stimulating effect on body tissues so a decrease will lead to a slowing of bodily functions. Onset of these symptoms is usually slow but can occur quickly such as after the removal of the thyroid gland. Because of the slow onset and the fact that sympoms are often attributed to other problems this condition can go undiagnosed for years. A complete list can be found on Table 50-5 p. 1264.

Myxedema coma is another complication. It is a medical emergency and can be fatal. It can be sudden or gradual in onset. Tempreture, blood pressure, pulse and respirations are all decreased and the patient enters a coma. Sudden onset myxedema can be caused by drugs, surgery, removal of the thyroid, cold or trauma. Treatment involves IV thyroid hormone and support of bodily function until the patient recovers.
 * Lethargy and fatigue. Patient may sleep much more than usual.
 * Confusion
 * Memory impairment
 * Apathy
 * Depressed mood. This disorder closely mimics depression in some. Patients can have all the symptoms of depression and be misdiagnosed.
 * Reduced temp, respiration, and blood pressure.
 * Bradycardia
 * Reduced deep tendon reflexes, clumsy
 * Reduced BMR
 * Anemic
 * Reduced need for O2
 * Weight gain
 * Constipation due to reduced intestinal movement.
 * Menorrhagia or amenohhria
 * Low libido
 * Elevated cholesterol and triglycerides
 * Decreased cardiac output (easily winded).
 * Always cold
 * Dry, leathery skin
 * Puffy hands and feet
 * Myxededma which is the accumulation of fatty deposits in the face and eyes. General appearrance is one of puffiness.

In the eldery the cognitive and emotional changes may be attributed to old age. This can cause misdiagnosis which leads to an unnecessary decline in quality of life and early placement in a nursing home. Eldery patients shoulc be screened for thyroid function if they have these symptoms.

Labs

Labs are very important in determining wheither hypothyroidism is primary, secondary or tertiary. TSH, T3 and T4 levels will change in different ways depending on the cause. In primary hypothyroidism TSH will be elevated while T3 and T4 are low. In secondary hypothyroidism TSH, T3 and T4 are all low. Tertiary hypothyroidism is diagnosed when an injection of TRH causes an increase an increase in TSH. Creatine Kinase, cholesterol and triglycerides are also elevated in hypothyroidism.

Normal lab values
 * TSH (Thyrotropin) - 0.4-4.2 mIU/L
 * T4 (Thyroxine) - Males 4-12 ug/dl Females 5-12 ug/dl. < 2 = Myxedema. > 20 = Thyroid Storm
 * T3 (Triodothyronine) - 70-205 ng/dl ages 20-50. Decreases with age.

Treatment
If caused by medication remove or change medications if possible.

Hypothyroidism will usually require lifelong replacement therapy. Levothyroxin (Synthroid) is pure T4 hormone and is the preferred drug for this condition. Dose ranges from 25-200 mcg. It should not be taken with iron, carafate or aluminum based antacids as these will decrease absorption. TSH levels are monitored every 4-6 weeks until they reach 0.5-2.5 mIU/L then every 6-12 months. Too much can cause an increase in Ca++. Patients should be monitored for cardiac irregularities especially the elderly and those with preexisting cardiac problems.

Liothyronine sidium (T3) and Liotrix (T3 adn T4 combination) may also be used. T3 has a much quicker peak action than T4.

Nursing Considerations
Assessment is important to identify problems early. Early detection and treatment can prevent most of the signs and symptoms listed above. Assess for changes in weight, mental function and energy levels as these are common early symptoms.

A low calorie diet can be recommended for those with weight gain. Reassure patient that weight gain may self correct one thyroid levels are returned to normal. High fiber, high water and low fat foods are good for those with constipation.

Once treatment begins assess for improvements to mental and physical energy levels. Also be sure and assess for cardiac irregularities especially in those with preexisting conditions. If patient is in a myxedema coma they will need cardiac support to maintain sufficient function. Frequent vital checks and administration of fluids.

Patient Education

 * Stress that this is a lifelong problem and will require daily medication to manage. Frequent checkups are also necessary.
 * Edlucate pateint what not to take with meds; iron, aluminum, carafate.
 * Skin care: lotion often soap seldom.
 * Avoid sedatives as these can have more of an effect on those with untreated hypothyroidism.
 * Levothyroxin may increase the actions of digoxin, SSRI's and anticoagulants. Teach patient signs of overdose for these meds and that a dose reduction may be necessary.
 * If taking insulin monitor blood sugar as insulin needs may increase as energy levels normalize
 * Teach signs of overdose: dyspnea, tachycardia, insomnia, restlessness, agitatio, tremors and to contact provider if they appear.