27 terms

Hypothyroidism

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Iodine deficiency
Rare in the US
Remains the most common cause of hypothyroidism worldwide
Hypothyroidism In areas of iodine sufficiency
Autoimmune disease (Hashimoto's thyroiditis)
Iatrogenic causes (treatment of hyperthyroidism) are most common
Etiology of hypothyroidism
Primary - Hashimotos thyroiditis
Iatrogenic-Hyperthyroid treatment
Drugs: iodine excess, contrast, hyperthyroid treatment
Congenital hypothyroidism
Secondary Hypothyroidism
Hypopituitarism:
Hypothalamic disorders
Associated autoimmune diseases of hypothyroidism
Rheumatoid arthritis
Diabetes Mellitus 1
Pernicious anemia
Sjogren's
Vitiligo (loss of hair color)
Hypoparathyroidism
Geography of hypothyroidism
Incidence is ten times higher than average in iodine-deficient areas
*places where there is excessive consumption of goitrogens (e.g. cassava)
Symptoms of hypothyroidism
Tiredness, weakness
Dry skin
Feeling cold
Hair loss
Constipation
Weight gain with poor appetite
Dyspnea
Hoarse voice
Menorrhagia (later oligomenorrhea or amenorrhea)
Paresthesia
Impaired hearing
Difficulty concentrating and poor memory
Signs
Dry coarse skin; cool peripheral extremities
Puffy face, hands- Myxedema
Non pitting edema
Lower extremities - pitting edema
Diffuse alopecia
Bradycardia
Peripheral edema
Delayed tendon reflex relaxation
Carpal tunnel syndrome
Serous cavity effusions
Hashimoto's thyroiditis - present with
with a goiter rather than symptoms of hypothyroidism
Goiter may not be large
Usually irregular and firm
Often possible to palpate a pyramidal lobe
Subclinical hypothyroidism
Depression
Cognitive problems
Weight gain
Fatigue
Irregular menstruation
Infertility
Mild thyroid failure
Gastrointestinal disease
Hyperlipidemia
Coronary artery disease
Hypertension
Neonatal/congenital hypothyroidism
Prolonged jaundice
Hoarse cry
Constipation
Somnolence
Feeding problems
Impaired mental development
Short stature
Protruding abdomen with an umbilical hernia
Juvenile/infantile hypothyroidism
Some signs shared with adult hypothyroidism
Linear growth retarded
Delayed puberty
Delayed union of epiphyses
Iatrogenic hypothyroidism
In the first 3 to 4 months after radioiodine treatment, transient hypothyroidism may occur due to reversible radiation damage rather than to cellular destruction
Secondary hypothyroidism
Isolated TSH deficiency is very rare, usually with other anterior pituitary hormon deficiencies
Diagnosis of Secondary hypothyroidism
low unbound T4 level
Chronic iodine excess
chronic iodine excess can also induce goiter and hypothyroidism
Evaluation of Hypothyroidism
raised TSH levels
decreased free T4 levels
primary test in diagnosis of hypothyroidism
TSH
Thyroid autoantibody
Positive result - in 95% of patients with autoimmune thyroiditis
Treatment of hypothyroidism
Levothyroxine (T4)
*Usually started at a dose between 25-75mcg, and titrated to target
Takes 4-6 weeks for TSH blood level to adjust after a change in dose
Liothryonine
May be prescribed in post-thyroidectomy patients to minimize the amount of time they need to be off thyroid replacement therapy before an iodine scan
Levothyroxine
The American Association of Clinical Endocrinologists (AACE) advocates the use of a high-quality brand preparation of levothyroxine
Myxedema coma
High mortality rate
Myxedema coma almost always occurs in the elderly
non compliance with hypothyroid treatment
*Extreme hypothermia: 75.2-90°F (24-32.2°C)
*Somnolence leading to stupor and coma
Myxedema madness
Frank psychosis
Myxedema heart disease
Enlarged due to dilation and pericardial effusion
Myxedema Coma Treatment
Warmed with blankets - only if < 30º
But - too rapid warming increases the risk of cardiac arrhythmias
Airway management and ventilatory support - prevent respiratory failure
Intravenous levothyroxine
Parenteral hydrocortisone - prevents adrenal crisis
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