Podcast: Play in new window | Download

Disorders of the Thyroid

• Hormones
  • TSH = thyroid stimulating hormone
    • Created and secreted by the anterior pituitary
  • T4 = thyroxine
  • T3 = triiodothyronine
• Primary caused by disease in the thyroid
• Secondary Caused by diseases in the hypothalamus or pituitary

Hyperthyroidism

• Elevated levels of free T4 and T3
• Amiodarone may cause thyrotoxicosis

Causes

• Graves disease
  • The most common cause of hyperthyroidism accounting for between 50–80%
  • An autoimmune disease
  • The body creates antibodies that bond to the receptor for thyroid stimulating hormone and stimulates production of T4 and T3.
• Thyroiditis
  • Inflammation of thyroid

Clinical Presentation & Physical Exam findings

-Thyroid
– Goiter or palpable thyroid nodule
– May be tender

• Eyes
  • Stare
  • Lid lag with downward gaze
  • Upper eyelid retraction
  • Exophthalmos
  • Diplopia
• Heart
  • Tachycardia
  • A-Fib
  • Palpitations
  • Chest pain
• Skin
  • Fine hair
  • Warm
  • Moist
  • Onycholysis
  • Pretibial Myxedema
• Mental changes
  -Irritability
  • Nervousness
• Other
  • Fatigue
  • Heat intolerance
  • Sweating
  • Changes in weight
  • Increase in appetite
  • Loose stool
  • Frequent urination
  • Muscle cramps
  • Changes in menstruation
  • Fine resting tremor
  • Hyperreflexia
  • Insomnia

Labs & Studies

• Blood work
  • TSH (thyroid stimulating hormone) decreased (almost all the time)
  • T4 (thyroxine) elevated
  • T3 (triiodothyronine ) elevated
  • ESR elevated
  • TSH receptor antibody elevated in Grave’s disease
• Radioactive iodine uptake scan
• U/S – increased blood flow

Treatment

• Beta blockers
  • Propranolol, atenolol, metoprolol
• Methimazole and propylthiouracil (PTU)
  • Inhibit production of T3 and conversion to T4
  • Used to prepare patients for surgery
  • Used to treat patients who can not do either iodine ablation or have surgery.
• Radioactive Iodine ablation
• Surgical removal

Thyroid storm

• Very rare
• Life threatening emergency
• Typically in untreated patients with Grave’s Disease or multi-nodular goiter

Risk factors

• Infection
• Surgery
• Trauma
• Preeclampsia

Clinical presentation

• Fever
• Tachycardia
• Vomiting/diarrhea
• Dehydration
• Muscle weakness
• Confusion

Labs & Studies

• Blood work
  • TSH (thyroid stimulating hormone) decreased (almost all the time)
  • T4 (thyroxine) elevated
  • T3 (triiodothyronine ) elevated
  • ESR elevated
  • TSH receptor antibody elevated in Graves disease
  • BMP
• U/S

Treatment

• Propylthiouracil and iodine
• Propranolol
• IV fluids
• Cooling blanket
• Corticosteroids

Hypothyroidism

Causes

• Thyroiditis
• Patient has no thyroid
  • Radioactive iodine ablation
  • Surgical removal of the thyroid
• Congenital
• Medications
  • Amiodarone which is structurally similar to thyroxine
  • Lithium
  • Propylthiouracil (PTU) and Methimazole – used to control hyperthyroidism

Clinical Presentation

• Cold intolerance
• Slow speech
• Hoarse voice
• Paresthesias
• Puffy face
• Fatigue
• Changes in menstrual cycle, typically heavier but may also cause amenorrhea
• Pale, cool, dry skin
• Thin brittle nails and hair
• Poor memory
• Depression
• Psychosis
• Dementia
• Weakness
• Muscle stiffness
• Anorexia
• Constipation
• Weight gain
• Edema
• Bradycardia
• Hyporeflexia

Labs & Studies

• Blood work
  • TSH elevated in primary hypothyroidism.
  • T4 decreased
  • T3 may be normal
• Antithyroid peroxidase
• Antithyroglobulin antibodies
• CBC may show anemia, normocytic-normochromic
• BMP low sodium

Treatment

• Thyroid hormone replacement
  • Levothyroxine is the most commonly used medication. It is a synthetic T4.
  • Patients are started with the lowest dose and it is slowly moved up while monitoring symptoms and TSH levels.
  • Once the dose is set yearly levels should be checked
  • Treatment is forever
  • Monitor for symptoms of hyperthyroidism

Myxedema

• The mirror of thyroid storm. This is extremely severe hypothyroid and a true life threatening emergency

Clinical Presentation

• Patients with myxedema will have symptoms of hypothyroid as well as
  • Mental changes from confusion to coma
  • Convulsions
  • Hypotension
  • Hypothermia
  • Hypoventilation
  • Rhabdomyolysis and acute kidney damage
  • Hyponatremia

Treatment

• IV levothyroxine
• Intubation if necessary
• Slow warming if necessary