1. Acquired Hypothyroidism
Katrina L. Parker, MD

2. 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

4. 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

5. Etiology Autoimmune disease Delayed onset congenital hypothyroidism
Iodine deficiency
Medications
Anti depressants
Lithium
Amiodarone % of patients
Radiation therapy
Radioactive iodine therapy
Thyroid surgery

6. Causes of Acquired Hypothyroidism
Thyroidectomy or radioiodine therapy
Thyroid cancer
Thyroxicosis
Lingual thyroid
Isolated midline thyroid
TRH deficiency
Pituitary disorder
Chronic infections
Idiopathic

7. Etiology Environmental factors High iodine intake Selenium deficiency
Pollutants – tobacco smoke
Infectious disease- chronic hepatits C

8. 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

9. 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

10. Absorption of thyroid hormone
Affected by
Iron supplements
Questran
Antacids containing Aluminum hydroxides
Calcium supplements
Soy products
Rifampin
Anti convulsants

11. 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

12. Hypothyroidism and Concurrent Conditions
Depression
Euthyroid sick syndrome
Starvation
Critically ill
Corticosteroids and dopamine
Infertility

13. Differential Diagnosis
Primary versus hypothalamic failure
Short stature
Coarse features R/O
Down Syndrome
Hurler & Hunter Syndrome
Generalized gangliosidosis

15. 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

17. 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

18. 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

20. 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

23. Delayed closure of fontanelles
Delayed dental eruption
Delayed epiphyseal development
Menometrorrhagia or galactorrhea

24. 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

25. 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

26. 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

27. 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

28. Glandular Concentrates
Sold in health food stores
Are not regulated by the FDA
Potency is not guaranteed

29. QUESTIONS