Notes by A.J. Chandrasekhar (3/10/08)

To be read only after you have made an attempt to answer questions on your own by reading books and literature.

Hypothyroidism

List common symptoms of hypothyroidism.

Answer

  • Weakness
  • Fatigue
  • Memory impairment
  • Cold intolerance
  • Constipation
  • Loss of hair
  • Hoarseness
  • Deafness
  • Menstrual irregularity

What are the physical findings of a patient with hypothyroidism?

Answer

  • Dry coarse skin
  • Periorbital edema
  • Coarse thin skin
  • Thick tongue
  • Slow speech
  • Deep voice
  • Delayed  Achilles' tendon reflex time
  • Bradycardia

What are the common etiologies for primary hypothyroidism?

Answer

Primary hypothyroidism

  • Hashimotto's thyroiditis 
  • Idiopathic
  • Post therapy for hyperthyroidism
  • External beam radiotherapy 
  • Lithium, Amiodarone
  • Iodide deficiency 

What historical information will help you in identifying the etiology for primary hypothyroidism?

Answer

  • Hashimotto's thyroiditis 
    • Family history or the presence in the patient of other autoimmune endocrine disease
    • Schmidt's syndrome / Hashimotto's and pernicious anemia and diabetes mellitus
  • Idiopathic
  • Post therapy for hyperthyroidism
    • Radioactive iodine therapy / History of radioactive iodine therapy
    • Subtotal thyroidectomy / History of thyroidectomy
  • External beam radiotherapy /  history of neck radiation for lymphoma or head and neck cancer
  • Lithium, amiodarone
  • Iodide deficiency / underdeveloped countries

How does physical examination of the thyroid gland help in the differential diagnosis of hypothyroidism?

Answer

  • Hashimotto's thyroiditis 
    • enlarged thyroid
  • Idiopathic
    • atrophic thyroid
  • Post therapy for hyperthyroidism
    • depends on etiology
  • External beam radiotherapy
    • radiation changes over thyroid (pigmentation, induration)
  • Lithium, Amiodarone
    • goiter
  • Iodide deficiency 
    • goiter

What are the common etiologies for secondary hypothyroidism?

Answer

  • Hypothalamic dysfunction
  • Pituitary dysfunction  

What are the common etiologies for secondary hypothyroidism due to hypothalamic dysfunction?

Answer

  • Therapeutic irradiation
  • Hypothalamic tumors
    • germinoma
    • meningioma
    • hamartoma

What are the symptoms and signs that would alert you to the possibility of hypothalamic lesion?

Answer

  • Diabetes insipidus
  • Narcolepsy
  • Excessive appetite 
  • Marked anorexia
  • Hyperthermia
  • Marked hypothermia

What are the common etiologies for secondary hypothyroidism due to pituitary dysfunction?

Answer

  • Pituitary dysfunction /secondary adrenal insufficiency, hypogonadism, growth hormone deficiency
    • Pituitary tumor 
    • Post partum pituitary necrosis
    • Sarcoidosis 
    • Metastatic carcinoma involving pituitary, hypothalamus or stalk 
    • Rathke's cleft cyst, craniopharyngioma, carotid artery aneurysm compressing pituitary

What are the signs and symptoms that would suggest pituitary tumor?

Answer

Space-occupying mass of pituitary 

  • Headache
  • Bitemporal hemianopsia
  • 3rd, 4th, or 6th nerve defects
  • Seizures
  • Rhinorrhea
  • Meningitis

What would make you suspect postpartum pituitary necrosis as the etiology for pituitary dysfunction?

Answer

  • History of shock or massive hemorrhage at time of delivery
  • Inability to breast feed
  • Amenorrhea afterwards

Which tests would help confirm the diagnosis of hypothyroidism?

Answer

  • Total T4:  Low
  • Free T4: Low
  • TSH
  • Free T3:  of no value

Which lab test helps you to distinguish primary from secondary hypothyroidism?

Answer

  • TSH
    • increased / primary
    • decreased / secondary
  • Baseline and dynamic anterior pituitary hormone testing for deficiencies and overproduction

How do you distinguish hypothalamic from pituitary dysfunction as the etiology for secondary hypothyroidism?

Answer

TRH stimulation: 

  • Primary:  Exaggerated TSH response. TSH levels increase up to 15
  • Pituitary: Flat TSH response
  • Hypothalamus: Normal TSH response

Which tests helpful in the diagnosis of identifying a pituitary mass?

Answer

  • MRI with gadolinium enhancement to document the presence of a mass
  • Testing for other tumor markers (alpha subunits)

What are the common non-specific lab abnormalities of hypothyroidism?

Answer

  • CPK
  • Anemia
  • Bradycardia, low voltage and non specific ST T wave changes
  • Hypoxia with hypercapnea

What are the treatment options for primary hypothyroidism?

Answer

  • Thyroid hormone replacement therapy with non-generic l-thyroxin or a generic form that has undergone rigorous quality controlled supervision of the manufacturing process. 
  • With risk factors for coronary arterial disease, it would be wise to start with a low dose of thyroid hormone and increase the dose slowly.

What are the treatment options for secondary hypothyroidism?

Answer

  • Evaluate if secondary hypoadrenalism is present 
  • If preset, treat simultaneously with the treatment of the hypothyroidism 
  • Also evaluate whether hypogonadism and/or growth hormone deficiency is present and treat accordingly
  • Then treat the cause of the secondary hypothyroidism 

What are the components of total serum thyroxin?

Answer

  • Free thyroxine 0.03%
  • Thyroxine binding albumin 10%
  • Thyroxine binding prealbumin 20%
  • Thyroxine binding globulin 70%

Alterations in these binding proteins can alter serum thyroxine values and mistaken diagnosis of hypo or hyperthyroidism can be made.

Describe euthyroid hypothyroxinemia / sick syndrome.

Answer

  • Clinical picture
  • Normal sized thyroid gland
  • Low serum TBG
  • Hypoalbuminemia / nephrotic syndrome, cirrhosis
  • Low serum total T4
  • Normal free T4
  • Normal TSH
  • Normal TSH response to TRH 

What is sub clinical hypothyroidism?

Answer

  • Euthyroid
  • Normal serum T4 and T3
  • Elevated TSH

Hyperthyroidism

What are the symptoms of hyperthyroidism?

Answer

Symptoms: Potentiation of sympathetic system by excess thyroxine

  • Nervousness
  • Heat intolerance
  • Palpitations
  • Tremor
  • Weight loss in spite of voracious appetite
  • Weakness particularly proximal muscle group
  • Hyper defecation

What are the physical findings of hyperthyroidism?

Answer

  • Thyroid enlargement
    • pyramidal lobe
    • bruit
  • Potentiation of sympathetic system by excess thyroxine
    • lid lag
    • warm moist skin
    • fine tremor
    • brisk reflexes
    • tachycardia
  • Onycholysis / Plumber's nails
  • Mucopolysaccharide infiltration
    • proptosis
    • ophthalmopathy: diplopia
    • pretibial myxedema 
    • clubbing/ thyroid acropachy

What are the common etiologies for hyperthyroidism?

Answer

·         Grave's disease

·         Toxic multinodular goiter

·         Toxic adenoma

·         Factitious thyrotoxicosis

·         Toxic struma ovari

·         Thyroiditis

How does physical examination of the thyroid help in the differential diagnosis of hyperthyroidism?

Answer

·         Graves disease

o        diffuse enlargement

o        bruit

·         Toxic multinodular goiter

o        multiple nodules

·         Toxic adenoma

o        single nodule

·         Factitious thyrotoxicosis

o        small thyroid

·         Toxic struma ovari

o        small thyroid

·         Thyroiditis

o        diffuse enlargement

  What tests are useful to confirm hyperthyroidism?

Answer

  • Total T4:  high
  • Free T4: High
  • Free T3:  High
  • TSH: Decreased

What are the tests useful to distinguish Grave's disease from other causes?

Answer

  • RAIU/ Scintiscan
    • increased uptake / symmetrical goiter / Graves
    • heterogynous uptake / asymmetric / thyroiditis, multinodular goiter
    • hot nodule / toxic adenoma
    • decreased / factitious and struma ovari and thyroiditis
  • TRAb
  • TSI
  • Thyroid auto antibodies are insensitive
  • TRH stimulation: flat TSH response in Grave's disease

Describe the lab findings in a patient with euthyroid hyperthyroxinemia, related to alteration in TBG.

Answer

  • High serum TBG
  • Estrogens hepatitis, 5-fluorouracil
  • High serum total T4
  • Normal free T4
  • Normal TSH

Describe the clinical and  lab findings in a patient with euthyroid hyperthyroxinemia, unrelated to TBG levels.

Answer

  • Clinical picture
  • Acute non-thyroidal illness, psychiatric illness, drugs
  • Normal sized thyroid gland
  • High serum total T4
  • High free T4
  • Unrelated to TBG

What are the treatment options for hyperthyroidism?

Answer

  • Antithyroid drug therapy
  • Radioactive iodine therapy
  • Surgery
  • Symptomatic therapy with beta blockers

What are the treatment options based on the etiology?

Answer

  • Graves disease
    • Induce euthyroid state with antithyroid drug therapy first
    • Radioactive iodine therapy
      • majority preferred form of treatment
    • Surgery
      • for children
      • large goiter
  • Toxic  multinodular goiter
    • Induce euthyroid state with antithyroid drug therapy first
    • Radioactive iodine therapy
      • majority
    • Surgery  
      • large goiter
      • pressure complications from goiter
  • Toxic adenoma
    • Radioactive iodine therapy or
    • Surgery
  • Thyroiditis / symptomatic therapy only
  • Factitious thyrotoxicosis / treat the personality problem

How would you treat a pregnant patient with hyperthyroidism?

Answer

  • Treat with antithyroid drugs only
  • Surgery is rarely indicated
  • Radioactive iodine therapy should never be used
  • Close monitoring of newborn for thyroid function