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Acquired Hypothyroidism
Katrina L. Parker, MD
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Acquired Hypothyroidism
The thyroid gland makes too little or no thyroid hormone Occurs anytime during childhood Usually affects infants starting at 6 months of age
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Historical Review 1912 Dr. Hakaru Hashimoto described 4 patients with a chronic disorder of the thyroid He termed it struma lymphomatosa The thyroid glands had Fibrosis Diffuse lymphocytic infiltation Parenchymal atrophy Eosinophilic changes
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Etiology Autoimmune disease Delayed onset congenital hypothyroidism
Iodine deficiency Medications Anti depressants Lithium Amiodarone % of patients Radiation therapy Radioactive iodine therapy Thyroid surgery
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Causes of Acquired Hypothyroidism
Thyroidectomy or radioiodine therapy Thyroid cancer Thyroxicosis Lingual thyroid Isolated midline thyroid TRH deficiency Pituitary disorder Chronic infections Idiopathic
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Etiology Environmental factors High iodine intake Selenium deficiency
Pollutants – tobacco smoke Infectious disease- chronic hepatits C
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Incidence 0.3 to 1.5 cases per 1000 population per year
15-20 times more frequent in women than men in families with hypothyroidism or autoimmune disease Associated with other autoimmune diseases Type 1 DM Celiac disease Type 2 and Type 3 polyglandular autoimmune disorders
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Prevalence Annual incidence 4 per 100 women and 1 per 1000 men
More common in certain populations sporadic inheritance, sometimes autosomal recessive post-partum thyroiditis affects 5% of women
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Absorption of thyroid hormone
Affected by Iron supplements Questran Antacids containing Aluminum hydroxides Calcium supplements Soy products Rifampin Anti convulsants
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Hypothyroidism Classification
TYPE Origin Description Primary Thyroid gland The most common form is Hashimoto thyroiditis Secondary Pituitary Gland Occurs if the pituitary does not create enough TSH Tertiary Hypothalamus The hypothalamus fails to produce sufficient TRH
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Hypothyroidism and Concurrent Conditions
Depression Euthyroid sick syndrome Starvation Critically ill Corticosteroids and dopamine Infertility
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Differential Diagnosis
Primary versus hypothalamic failure Short stature Coarse features R/O Down Syndrome Hurler & Hunter Syndrome Generalized gangliosidosis
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Presentation of Hashimoto’s Thyroiditis
Euthyroidism and goiter Subclinical hypothyroidism and goiter Primary thyroid failure Adolescent goiter Painless thyroiditis or silent thyroiditis Postpartum painless thyrotoxicosis Alternating hypo- and hyperthyroidism
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Signs Depression Physical & mental sluggishness Dry skin Constipation
Weight gain with poor appetite Dyspnea Poor muscle tone Menorrhagia Diminished sweating Hoarse voice or cry/large tongue
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Signs Coarse, dry skin Cool peripheral extremities
Puffy face, hands and feet (myxedema) Bradycardia Peripheral edema Delayed tendon reflex relaxation Carpal tunnel syndrome Mild unexplained weight gain NOT morbid obesity
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Skin – dry, thick, scaly, coarse
Hair- brittle, dry, coarse, excessive Lateral thinning of the eyebrows Prominent axillary & supraclavicular fat pads in infants Growth changes – short stature, infantile skeletal proportions with relatively short extremities Infantile naso-orbital configuration Delayed epiphyseal development
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Delayed closure of fontanelles
Delayed dental eruption Delayed epiphyseal development Menometrorrhagia or galactorrhea
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Labs Decreased TT4 and FT4, elevated TSH Thyroid antibodies
Anti- Thyroglobulin and anti thyroid perioxidase (TPO) R/O TBG deficiency Normocytic anemia Elevated cholesterol and carotene in childhood but normal or low in infants Decreased GH levels
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Imaging Skeletal maturation is delayed Ossification centers of the hip
Single stippled Multiple small areas Anterior beaking of the vertebrae Coxa vara & coxa plana Thyroid scan or ultrasound
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Treatment Levothyroxine
The drug of choice Dosage infants mg/kg/day Long standing hypothyroidism start with a low dose of ug daily and gradually increase Monitor TSH and FreeT4
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Treatment T4 only T4 and T3 in combination Desiccated Thyroid Extract
Currently the standard treatment Involves supplementation of levothyroxine alone T4 and T3 in combination Involves administering both synthetic L-T4 and L-T3 simultaneously in combination Desiccated Thyroid Extract animal based thyroid extract contains natural forms of l-t4 and l-t3e
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Glandular Concentrates
Sold in health food stores Are not regulated by the FDA Potency is not guaranteed
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QUESTIONS
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