Thyroid and Parathyroid

Laboratory Findings
Hypothyroidism is characterized by low circulating levels of T4 and T3. Raised TSH
levels are found in primary thyroid failure, whereas in secondary hypothyroidism
TSH levels are low. Secondary hyperthyroidism is rare and can be diagnosed by
measuring TSH after a TRH challenge. The TSH level is low and does not increase in
response to TRH. Autoimmune thyroid disease is characterized by the presence of
thyroid autoantibodies (antithyroglobulin, antimitochondrial, or anti–thyroidperoxidase
[anti- TPO]). Other findings in hypothyroidism include anemia,
diminished voltage with flattening or inversion of T waves on electrocardiogram,
slow alpha waves with loss of amplitude on electroencephalogram, and raised levels
of serum cholesterol (>300 mg/dL). In myxedema, comatose patients also have
. hyponatremia and CO2 retention
Treatment
Treatment of hypothyroidism is simple, inexpensive, and effective. Thyroxine is the
treatment of choice and is administered in dosages varying from 50 mg to 200 mg per
day. Patients are instructed to take tablets in the morning, usually without other
medications, or at mealtime to assure good absorption and to avoid any sleep
. interference
Young and otherwise healthy individuals tolerate initial starting doses of 100 mg of
thyroxine per day, but elderly patients, patients with coexisting heart disease, and
patients with profound hypothyroidism are less tolerant of thyroxine and should be
started on a lower dose, such as 25 mg to 50 mg, slowly increasing the dose over
weeks to months to attain a euthyroid state. An electrocardiogram should be obtained
before treatment of patients with severe hypothyroidism for comparison if chest pain
develops. Thyroxine dosage is titrated against TSH levels, which should return to
normal. Thyroxine supplementation also must be determined by the clinical response
of the patient. Whether or not patients with subclinical hypothyroidism (normal T4,
slightly raised TSH) should be treated is controversial. Evidence suggests that patients
with subclinical hypothyroidism and increased antithyroid antibody levels should be
treated, because they progress to more severe hypothyroidism. Patients with mild
hypothyroidism may benefit from small doses of T4, as the hypercholesterolemia,
. which accompanies hypothyroidism in this group of patients, is improved by therapy
Patients who present with myxedema coma, in contrast to the patients with mild to
moderate hypothyroidism, require emergency treatment with large doses of
intravenous thyroxine (400mg) followed by 100 mg/day. These patients usually are
. hyponatremic and hypocapnic and need careful monitoring in an intensive care unit
THYROIDITIS
( Autoimmune Lymphocytic Thyroiditis (Hashimoto's Thyroiditis
Chronic lymphocytic thyroiditis, more commonly known as Hashimoto's thyroiditis
or disease, after the physician who first described the condition in 1912, is an
autoimmune thyroid disease and is the most common cause of hypothyroidism. It is
ten times more common in women and more prevalent in the 30- to 60-year-old age
group, with a prevalence of about 20 cases per 1000 women and an annual incidence
of 1 to 2 new cases per 1000 women in the population. Autoimmune thyroiditis may
be familial; up to 50 percent of first-degree relatives of patients with chronic
autoimmune thyroiditis have thyroid antibodies inherited as a dominant trait. Chronic