Hypothyroid

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Hypothyroid

Clinical manifestations

There are a variety of signs and symptoms associated with hypothyroid, affecting all the systems of the body

Infant mentally retarded due to absence of TH stimulating brain tissue, due to the vast number of manifestations, I inserted this chart

Pathophysiology of other manifestations

Thyroid Carcinoma

Most common endocrine malignancy

Accounts for 60,220 cases a year with 1850 deaths

Ionizing radiation is most consistent causal factor

Congenital Hypothyroid

Deficiency present at birth

Present in 1 of every 3 to 4 thousand births

Hereditary defects in TH synthesis

Absent thyroid tissue

Sub-clinical hypothyrodism

4-8% of cases

Mild thyroid failure

Is an elevation in TSH level with normal levels of TH

Central (secondary) hypothyroidism

less common

Pituitary or hypothalamic failure with failure to stimulate normal thyroid function

Caused by pituitary tumors that compress surround pituitary cells

Also caused by treatment of theses tumors

Traumatic brain injury

Subarachnoid Hemorrhage

Pituitary infarction

Inadequate amounts of TSH or lack of TRH

Lack of negative feedback to hypothalamic release of TRH by TSH and TH

Low levels of TSH and TH and high levels of TRH

Primary Pathophysiology

Treatment

Hormone replacement therapy

Treatment of other symptpoms

Levothyroxine

Infants and children with hypothyroidism

Caused by congenital defects

Pituitary or thyroid gland

Loss of thyroid tissue leads to a decreased production of TH

Lack of TH negative feedback on pituitary TSH secretion and hypothalamic TRH secretion

Low levels of TH and high levels of TSH and TRH

Causes include

Endemic iodine deficiency

Most common cause worldwide

Rare in U.S due to iodized salt and fortified foods

Endemic goiter

Medications

Head and neck radiation therapy

Iatrogenic loss of thyroid tissue after surgical or radioactive treatment for hyperthroidism

Autoimmune thyroiditis (Hashimoto disease)

Most common cause in United States

Due to genetic disposition

associated with

IFN-A

chronic hepatitis C

smoking

Selenium deficinecy

High iodine intake

Gradual inflammatory destruction of thyroid tissue due to infiltration of

Induction of apoptosis

Antibody activation of natural killer cells

Auto reactive T lympocytes

Circulating thyroid autoantibodies

Lymphocytes