Hypothyroidism

From Encyclopedia Jr, free information reference for Kids

Hypothyroidism is the disease state in humans and domestic animals caused by insufficient production of thyroid hormone by the thyroid gland. There are several distinct causes for chronic hypothyroidism in human beings, the most common being Hashimoto's thyroiditis (an autoimmune disease) and radioiodine therapy for hyperthyroidism. Historically, iodine deficiency was the most common cause of hypothyroidism world-wide. Secondary hypothyroidism occurs if the pituitary gland is damaged by a tumor, radiation, or surgery so that it is no longer able to instruct the thyroid to make enough hormone^[1]. It is a relatively common disease in purebred domestic dogs as well, and can have a hereditary basis in dogs.

The severity of hypothyroidism varies widely. Patients are classified as "subclinical hypothyroid" if diagnostic findings show thyroid hormone abnormalities, but they do not exhibit any symptoms. Others have moderate symptoms that can be mistaken for other diseases and states. Advanced hypothyroidism may cause severe complications, the most serious one of which is myxedema.

Hypothyroidism results from sporadic inheritance, sometimes autosomal recessive. To diagnose the condition, levels of T4 (thyroxine) and TSH (thyroid stimulating hormone) are measured. The disease may also be caused by a lack of thyroid gland or pituitary hormone. Treatment comes in the form of thyroid hormone replacement therapy.

[edit] Signs and symptoms

Hypothyroidism has been called the "great imitator" for the vast number of medical conditions it can mimic. "Thyroid hormones are essential and primary regulators of the body's metabolism. Imbalances can affect virtually every metabolic process in the body, exerting significant effects on mood and energy level. Thyroid function has a profound impact on overall health via its modulation of carbohydrate, protein, and fat metabolism, vitamin utilization, mitochondrial function, digestive process, muscle and nerve activity, blood flow, oxygen utilization, hormone secretion, sexual and reproductive health, and many other physiological parameters" ^[2].

[edit] Adults

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• Slowed speech and a hoarse, breaking voice. Deepening of the voice can also be noticed.
• Impaired memory
• Impaired cognitive function (brain fog)
• Urticaria (hives)
• Migraine headache
• Increased sensitivity to heat and cold
• A slow heart rate with ECG changes including low voltage signals. Diminished cardiac output and decreased contractility.
• Pericardial effusions may occur.
• Sluggish reflexes
• Dry puffy skin, especially on the face, and hair loss, especially thinning of the outer third of the eyebrows
• Depression (especially in the elderly)
• Mild weight gain
• Anemia caused by impaired hemoglobin synthesis (decreased EPO levels), impaired intestinal iron and folate absorption or B12 deficiency from pernicious anemia
• Slowed metabolism
• Constipation
• Fatigue (physical)
• anxiety/panic attacks
• Choking sensation or difficulty swallowing
• Shortness of breath with a shallow and slow respiratory pattern.
• Impaired ventilatory responses to hypercapnia and hypoxia.
• Increased need for sleep
• Muscle cramps and joint pain
• Brittle fingernails
• Osteoporosis
• Paleness
• Irritability
• Yellowing of the skin due to impaired conversion of beta-carotene to vitamin A
• Abnormal menstrual cycles
• Impaired renal function with decreased GFR.
• Thin, fragile or absent cuticles
• Infertility or difficulty becoming pregnant
• Elevated serum cholesterol
• Acute psychosis (myxedema madness) is a rare presentation of hypothyroidism
• Poor muscle tone (muscle hypotonia)

[edit] Hypothyroidism in domestic dogs

Hypothyroidism in dogs is a slowly progressive disease as well and can be difficult to diagnose accurately in the early stages. Dogs with hypothyroidism are plagued by a number of health problems including recurring skin infections and lethargic behavior. Hypothyroidism in dogs may also progress to myxedema coma.

[edit] External links

• ATA Hypothyroidism Booklet
• American Thyroid Association
• American Association of Clinical Endocrinologists
• American Foundation of Thyroid Patients
• Thyroid Foundation of America

[edit] References

1. ^ ATA Hypothryoidism Booklet, pge 6, American Thyroid Association, 2003.
2. ^ Comprehensive Thyroid Assessment, [Geneva Diagnostics web site article]

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