Disorders of Thyroid Function

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Thyroid Disorders
Lori McCoy, DO

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What we will cover

• Hypothyroidism and Hyperthyroidism
• and the features, causes, workup and treatment of
  each

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Hypothalamic-Pituitary-Thyroid AxisNegative
Feedback Mechanism
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Hypothyroidism
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Hypothyroidism

• In the U.S. and other areas of the world with
  adequate iodine intake, the most common cause is
  autoimmune thyroid disease (Hashimotos).
• Occurs when the thyroid gland produces less than
  the normal amount of thyroid hormone
• May be temporary but usually is a permanent
  condition
• The frequency of hypothyroidism, goiters and
  thyroid nodules increases with age

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Hypothyroidism

• In its earliest stage, it may cause very few
• symptomsbut as thyroid hormone decreases
• and metabolism slows, patients may complain of
• fatigue forgetfulness brittle hair/nails
• dry skin constipation sore muscles
  
• weight gain heavy/irregular menses

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Hypothyroidism

• Typical causes include
• Autoimmune (Hashimotos)
• Treatment for hyperthyroidism
• Status post thyroid surgery or radiation
• Medication-induced
• Congenital disease
• Pituitary disorder

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Typical Thyroid Hormone Levels in Thyroid
Disease

• TSH T4 T3
• Hypothyroidism High Low Low
• Hyperthyroidism Low High High

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but what if

• TSH HIGH
• FREE T3 AND T4 NORMAL
• ..this is considered mild or subclinical
• hypothyroidism

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• Do assays for autoimmune/antibodies to thyroid
• peroxidase (TPO) and thyroglobulin (TG) If
  these are
• positive, this is Hashimotos Disease. 
• (About 1 out of 10 people who have
  mild/subclinical
• disease will go on to have hypothyroidism within
  3 years).

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May also consider.

• CBC, BMP, and FLP.which may show anemia,
• hyponatremia, hyperlipidemia and reversible
• increases in serum Cr. 

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As well as ordering

• Thyroid US
• ....then Fine Needle Aspiration if any suspicious
  nodules
• are found (remember thyroid nodules can be found
  in
• patients who are hypo-, eu-, or hyperthyroid).
• About 5-15 of solitary nodules will be
  malignant. 
•  

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Benign nodule
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Suspicious nodule with calcifications
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(No Transcript)
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Treatment of Hypothyroidism
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Hypothyroidism Treatment

• Levothyroxine (Synthroid) is the treatment of
  choice for
• the routine management of hypothyroidism.
• Adults Usual starting dose is 25 mcg/d
• Children up to 4.0 mcg/kg of body weight/d
• Elderly lt1.0 mcg/kg of body weight/d
• Clinical and biochemical evaluations at 6-8 week
  intervals until the
• serum TSH concentration returns to normal
• Take with full glass of water 30 minutes to 1
  hour before breakfast, on an empty stomach

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Primary Hypothyroidism Treatment Algorithm
Initial Levothyroxine Dose
6-8 Weeks
TSH gt3.0 ?IU/mL
TSH lt0.5 ?IU/mL
Repeat TSH Test
TSH 0.5- 2.0 ?IU/mL Symptoms Resolved
Increase Levothyroxine Dose by 12.5 to 25 mcg/d
Decrease Levothyroxine Dose by 12.5 to 25 mcg/d
Continue Dose
Measure TSH at 6 Months, Then Annually or When
Symptomatic
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Factors That May Reduce Levothyroxine
Effectiveness

• Drugs That Increase Clearance
• Rifampin
• Carbamazepine
• Phenytoin
• Factors That Reduce T4 to T3 Clearance
• Amiodarone
• Selenium deficiency
• Others
• Lovastatin and Sertraline

• Malabsorption Syndromes
• Gastric bypass surgery
• Short bowel syndrome
• Celiac disease
• Reduced Absorption
• Colestipol hydrochloride
• Sucralfate
• Ferrous sulfate
• Food (eg, soybean formula)
• Aluminum hydroxide
• Cholestyramine

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Hyperthyroidism
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hyperthyroidism

• Typical symptoms include
• nervousness and irritability palpitations
  
• heat intolerance and increased sweating
• tremors weight loss with increase in appetite
• frequent bowel movements
• Pretibial myxedema irregular menses
• insomnia
• Changes in vision, eye irritation or exophthalmos
•  

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Typical Thyroid Hormone Levels in Thyroid
Disease

• TSH T4 T3
• Hypothyroidism High Low Low
• Hyperthyroidism Low High High

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Hyperthyroidism

• Thyrotoxicosis will show suppressed TSH and
  elevated
• T3 and T4.   Subclinical hyperthyroidism has low
  TSH
• and normal T3 and T4.
• Some causes of hyperthyroidism
• Most common are toxic diffuse goiter (Graves
  disease), toxic multinodular goiter (Plummer
  disease), and toxic adenoma.
• Painful subacute thyroiditis
• Silent thyroiditis
• Iodine and iodine-containing drugs and
  radiographic contrast agents
• Exogenous thyroid hormone ingestion

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Further tests

• Check thyroid autoimmune/antibodies of
• thyroperoxidase (TPO), thyroglobulin (TG), and
• thyroid-stimulating immunoglobulin (TSI).
• Graves Disease will reveal very elevated TPO
• and TSI.
• Toxic multinodular goiter or Toxic adenoma will
  reveal low or absent TPO.

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Subclinical Hyperthyroidism
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Definition of Subclinical Hyperthyroidism

• Decreased TSH level
• Normal total or free serum T4 and T3 levels
• Few or no signs or symptoms of hyperthyroidism

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Potential Consequences of Subclinical
Hyperthyroidism

• Decreased bone density with increase risk of
  osteopenia or osteoporosis
• Increased risk of cardiac arrhythmias, especially
  in the elderly
• Increased risk of miscarriage in pregnancy
• May or may not have obvious symptoms!

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Should Subclinical Hyperthyroidism be Treated?

• Depends on the individual circumstances and
  presentation of the patient
• Usually will treat if TSH lt 0.1
• If TSH between 0.1 and 0.5
• May initially observe only and follow for
  development of overt hyperthyroidism (especially
  if young and otherwise healthy patient)
• Should consider treatment if evidence of
  potential complications of hyperthyroidism
  (especially if osteopenia/osteoporosis or a-fib
  is present)

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Treatment of Hyperthyroidism
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Treatment of Hyperthyroidism

• Methimazole (Tapazole) and Propylthiouracil
• (PTU) are meds of choice.
• Titrate dose every 6 weeks until thyroid levels
  normalize and the patient stabilizes. 
• Goal is to inhibit the synthesis of T3 and T4.

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Treatment of Hyperthyroidism

• Radioactive iodine therapy
• Iodine-131 taken up by functioning thyroid tissue
  to decrease thyroid hormone production, then
  fibrosis and destruction of the thyroid occurs
  over weeks to many months. Dose is intended to
  render the patient hypothyroid. Again, monitor
  thyroid levels q 6 weeks until levels are
  normalized.
• Surgical resection
• Remove hyperplastic and adenomatous tissues
• Restore normal thyroid function and,
  consequently, pituitary function

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Adjunctive Therapy of Hyperthyroidism

• Beta blockers
• Corticosteroid therapy
• Bile acid sequestrants (the enterohepatic
  circulation of thyroid hormones is increased in
  thyrotoxicosis. Bile-salt sequestrants bind
  thyroid hormones in the intestine and thereby
  increase their fecal excretion).
• Iodide

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Which Treatment to choose?

• Depends on
• Patient preference
• Severity of hyperthyroidism
• Evidence of complications of hyperthyroidism
• Pregnancy
• The cause of hyperthyroidism

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Thyroid storm

• AKA thyroid or thyrotoxic crisisacute,
  life-threatening,
• hypermetabolic state induced by excessive release
  of thyroid
• hormones in patients with thyrotoxicosis.
• Usually occurs in patients with untreated or
  partially treated thyrotoxicosis who experience a
  precipitating event like surgery, infection or
  trauma. 
• The clinical presentation includes fever,
  tachycardia,
• hypertension, neurological and GI abnormalities.
  HTN may be
• followed by CHF that is associated with
  hypotension and shock.

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Thyroid storm
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Osteopathic principles

• Can use OMT to treat somatic components of
  thyroid
• dysfunction
• Upper thoracic HVLA
• Thoracic inlet release
• Ribs 1 and 2
• C4-6 myofascial release
• Occipito-Atlantal myofascial release

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Questions?
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references

• UpToDate
• Journal of Endocrinology and Metabolism
• Clinical Endocrinology
• Thyroid.org