Oversecretion: Syndrome of Inappropriate Antidiuretic Hormone (SIADH)
Stimulates contraction of uterus at end of pregnancy (Pitocin®); release of milk from breast
ADH acts on kidney No ADH Present- Collecting Duct is NOT permeable to water and large volume of urine is produced ADH Present- Collecting Duct is permeable to water and a small volume of urine is produced
Measurement of Serum Thyroid Hormones: T3 by RIA. thyroxine (T4) represents 80% of the thyroid hormone produced by the normal gland and generally represents the overall function of the gland. The other 20% is triiodothyronine measured as T3 by RIA -(radioimmunoassay) . Measurement of both hormones provides an accurate evaluation of thyroid function.
The T3U value may be useful in interpreting the other thyroid hormone test results.
A higher-than-normal T4 value combined with a high T3U value usually confirms the presence of hyperthyroidism.
A higher-than-normal T4 value combined with a low T3U value often occurs during pregnancy or in women who take birth control pills.
A lower-than-normal T4 value combined with a low T3U value usually confirms the presence of hypothyroidism.
A lower-than-normal T4 value combined with an increased T3U value may indicate kidney disease or long-term (chronic) illness. This can also occur normally in some healthy individuals.
Measurement of Serum Thyroid Hormones: T4 by RIA. T4 by RIA (radioimmunoassay) is the most used thyroid test of all. The T4 reflects the amount of thyroxine in the blood. If the patient does not take any type of thyroid medication, this test is usually a good measure of thyroid function .
Thyroid Binding Globulin. Most of the thyroid hormones in the blood are attached to a protein called thyroid binding globulin (TBG). unexplained high or low T4, or T3, it may be due to an increase or decrease of TBG. falsely elevate or lower the T4 level. These people are frequently misdiagnosed as being hyperthyroid or hypothyroid, but they have no thyroid problem and need no treatment.
Lower than normal values may indicate hypothyroidism .
This can be caused by
thyroid disease (such as thyroiditis),
pituitary gland disease, or
destruction of the thyroid gland by surgery or radiation.
Hyperthyroidism Excess amount of free Thyroid hormone. The symptoms Heat intolerance, nervousness, increased irritability, palpitations, weight loss with the same or increased food intake, and increased frequency of defecation. hyperkinesis, warm moist skin, a prominent stare and lid lag. The neurological exam may show a fine tremor and a fast return phase for the deep tendon reflexes. The cardiac exam tachycardia, although atrial fibrillation is also common, a prominent S4, and flow murmurs. The thyroid gland may be diffusely enlarged, nodular, or even normal in size.
23 y/o woman presents with the chief complaint of nervousness. She has a one month history of increased nervousness associated with a short temper, crying easily, and tremor. In addition she states she has lost 25 pounds without dieting, and is always hot. Her eyes protrude and feel dry. TSH ? Total T4 ? T3 ?
Grave’s disease Is an autoimmune disease in which the immune system produces antibodies which stimulate the TSH receptors of the thyroid gland. The result is the non-suppressible overproduction of thyroid hormone, resulting in the clinical manifestations of hyperthyroidism.
Greater than normal values may indicate: Hyperthyroidism.
This can be caused by
goiter that contains one or more abnormal growths (nodules)
from receiving too much thyroid hormone medication.
Primary Hypo thyroidism Occurs when disease of the thyroid gland prevents it from producing adequate amounts of thyroid hormone. all metabolic processes slow down. Patients are often fatigued, and may also have depression, decreased intellectual function, and, rarely, overt psychosis. Cold intolerance, dry skin, and constipation. The heart rate is often slowed, as is the relaxation phase of deep tendon reflexes. The T4 and Free T4 is low and the TSH is always high (usually greater than 20 mU/L) . T3 may be low/normal.
43 y/o patient with the chief complaint of "decreased energy." She complains of fatigue, inability to finish tasks, sleeping more, yet always being tired. She has also noticed a decreased cold tolerance, constipation, and dryness of the skin. She comments that she is always cold, even in the summer. She has a positive family history for thyroid problems, but does not know the details TSH T3 T4
Secondary hypo thyroidism Failure of the thyroid gland due to the inadequate production of Thyroid Stimulating Hormone (TSH). This can occur due to primary failure of the pituitary or as the result of hypothalamic dysfunction (tertiary hypothyroidism). Pituitary failure can result from destruction by pituitary and non-pituitary tumors, head trauma, radiation, postpartum infarction (Sheehan’s syndrome) or unknown causes (idiopathic). Patients with secondary hypothyroidism must be evaluated for pituitary tumors and other hormone deficiencies.