-IBIS-1.5.0-
tx
endocrine system
hypothyroidism
diagnoses
definition and etiology
definition: A lack of thyroid hormone in the adult (aka "cretinism" in the child) and the characteristic presentation (archaically "myxedema").
etiology: Thyroid deficiency is quite common, officially affecting about 1% of the population, especially women. It is much underdiagnosed, and physicians have now observed many cases of subclinical hypothyroidism, where patients have hypothyroid symptoms and respond well to thyroid support, although measure normal on thyroid panels. Hypothyroidism tends to run in families.
The most common type of hypothyroidism, primary hypothyroidism, is usually a result of Hashimoto's thyroiditis, where the thyroid becomes shrunken and fibrotic with markedly diminished function.
Other causes of hypothyroidism include exposure to radioiodine; dietary goitrogens (brassica family, particularly); antithyroid drugs; thyroidectomy; DeQuervain's thyroiditis; suprathyroid disease; congenital absence, hypoplasia or ectopia of the gland; pituitary or hypothalamic failure/imbalance.
Typically, the onset of hypothyroidism is insidious and gradually progressive: often the patient, family and physician may not notice its development. Symptom expression ranges from clinically frank to clinically undetectable.
In the infant, symptoms may be evident at birth, but usually develop in the first few months of life, depending upon the extent of thyroid deficiency. It appears in about 1 in 5000 neonates.
signs and symptoms
signs and symptoms:
infant/child:
Extended physiologic jaundice.
Constipation.
Somnolence.
Hoarse cry.
Feeding difficulties.
Failure to reach expected milestones of development.
As the child grows he/she manifests the typical physical appearance of the cretin: short stature; protruding tongue; widely set eyes; sparse hair; dry skin; protuberant abdomen with umbilical hernia; broad flat nose; decreased mental development; impaired sexual maturation at puberty; and poor school performance.
adult:
Cold intolerance.
Dry skin and hair.
Constipation.
Heavy menses.
Facial puffiness and paleness.
Deep, monotonous voice.
Tingling hands (carpal tunnel syndrome).
Decreased libido.
Decreased energy.
Mental slowness, confusion, lethargy, apathy.
Dull, expressionless look.
Possible goiter.
Decreased Achilles reflex return.
Decreased basal body temperature: 97°F or below on first a.m. reading.
lab findings:
Decreased serum T4: although it may be normal.
may see decreased T3U.
Decreased FT4I.
Increased TSH: though this is not specific for hypothyroidism, and may be normal.
Increased serum cholesterol.
T3 assay will often be normal (from increased TSH).
TRH stimulation test for secondary hypothyroidism: if TSH rises, the patient has a hypothalamic disease; if TSH does not rise, then it is diagnostic for pituitary disease.
Hypothyroidism from sympathetic excess/adrenocortical compensation will show low T3 and borderline high T4; treatment with exogenous thyroid eventually stops being effective. (Easley)
Liver enzymes may be mildly increased.
course and prognosis
With proper replacement therapy, usually by either the synthetic hormone or thyroid extract, USP, the prognosis is excellent, although carpal tunnel syndrome may take up to a year to clear. In children, it is imperative that therapy begin as soon as possible to avoid irreversible impairment of mental and/or physical development.
The major complication is myxedema coma: hypothermic, stuporous coma: a possible sequela of an untreated patient with severe hypothyroid disease.
differential diagnosis
Simple obesity
Down's syndrome: can be confused with cretinism in children.
Chronic nephritis or the nephrotic syndrome: can be confused with myxedema.
Consider sympathetic nervous system excess related to low hormone levels (e.g. estrogen), or glycogen or glucagon disorder. (Easley)
Dementia.
Failure to thrive.
footnotes