Coupon Accepted Successfully!



Table - Causes of Hypothyroidism (Ref. Hari. 18th ed., Pg-2918, table 341.4)


  1. Primary
  1. Autoimmune hypothyroidism: Hashimoto's thyroiditis, atrophic thyroiditis
  2. Iatrogenic: 131I treatment, subtotal or total thyroidectomy, external irradiation of neck for lymphoma or cancer
  3. Drugs: iodine excess (including iodine-containing contrast media and amiodarone), lithium (LQ 2012), antithyroid drugs, p-aminosalicyclic acid, interferon-α
  4. Congenital hypothyroidism: absent or ectopic thyroid gland, dyshormonogenesis
  5. Infiltrative disorders: amyloidosis, sarcoidosis, hemochromatosis (LQ 2012), scleroderma (LQ 2012), cystinosis, Riedel's thyroiditis


  1. Silent thyroiditis, including postpartum thyroiditis
  2. Subacute thyroiditis
  3. Withdrawal of thyroxine treatment in individuals with an intact thyroid
  4. After 131I treatment or subtotal thyroidectomy for Graves' disease
  1. Secondary
  1. Hypopituitarism: tumors, pituitary surgery or irradiation, infiltrative disorders, Sheehan's syndrome, trauma, genetic forms of combined pituitary hormone deficiencies
  2. Isolated TSH deficiency or inactivity
  3. Hypothalamic disease: tumors, trauma, infiltrative disorders, idiopathic

Symptoms of hypothyroid:
Tiredness, lethargy, depression, cold intolerance, weight gain, constipation, menorrhagia, hoarse voice, poor cognition/dementia, myalgia.


  1. Bradycardia, (FAQ)
  2. Dry skin and hair, toad like face
  3. Non-pitting oedema (LQ 2012),
  4. Cerebellar ataxia, (MCQ)
  5. Ankle Jerk relaxation is delayed (Hung up reflex) & pseudomyotonia
  6. 'Toad-like face.
  7. There may be goitre depending on the cause,
  8. Signs of CCF
  9. Pericardial effusion.
  10. Prolactin levels are often modestly increased and may contribute to alterations in libido and fertility and causes galactorrhea (Ref. Hari. 18th ed., pg - 2920)
  11. Fluid accumulate in the middle ear, giving rise to conductive deafness.
  12. Carpal tunnel and other entrapment syndromes are common
Extra Edge :

Peripheral neuropathy is very uncommon

Other lab findings in Hypothyroidism

  1. Raised serum enzymes
    1. creatine kinase,
    2. aspartate aminotransferase,
    3. LDH
  2. Hypercholesterolemia (LQ 2012)
  3. Anaemia  - Normochromic normocytic or macrocytic
  4. Hyponatraemia – due to SIADH.


  1.  T3 T4 and TSH due to lack from the pituitary (Secondary hypothyroidism).
  2. TSH, T4,  T3 (in Primary hypothyroidism):
  3. Increase LDL Cholesterol (FAQ)
  4. Normochromic macrocytic anaemia or dimorphic anemia or sideroblastic anemia can occur. (FAQ)


  1. Young: Levothyroxine (T 4) (Full dose from day 1)
  2. Elderly or ischemic heart disease: Start with low dose 25 microg/24h; dose by 25microg/4wks
  3. Subclinical thyroid disease
    1. Subclinical hypothyroidism suspect if TSH, with normal T4 and T3, and no obvious symptoms. (FAQ)
    2. Management: Treat with thyroxine. 

Situations in which an adjustment of the dose of levothyroxine may be necessary

  1. Increased dose required with Use of other medication
    1. Increase T4 clearance
      1. Phenobarbital                  
      2. Phenytoin                        
      3. Carbamazepine
      4. Rifampicin                        
      5. Sertraline                          
      6. Chloroquine
    2. Interfere with intestinal T4 absorption
      1. Cholestyramine                
      2. Sucralfate                                          
      3. Aluminium hydroxide
      4. Ferrous sulphate            
      5. Dietary fibre supplements            
      6. Calcium carbonate
    3. Pregnancy or oestrogen therapy
      1. Increases concentration of serum thyroxine-binding globulin 
    4. After surgical or 131I ablation of Graves' disease
      1. Reduces thyroidal secretion with time
    5. Malabsorption, e.g. coeliac disease  
  2. Decreased dose required
    1. Ageing 
      1. Decreases T4 clearance
    2. Graves' disease developing in patient with long-standing primary hypothyroidism
      1. Switch from production of blocking to stimulating TSH receptor antibodies


Table 335-8 Causes of Thyroiditis (Ref. Hari. 18th ed.Table 341.8 Pg-2928)

  1. Acute
  1. Bacterial infection: especially Staphylococcus, Streptococcus, and Enterobacter
  2. Fungal infection: Aspergillus, Candida, Coccidioides, Histoplasma, and Pneumocystis
  3. Radiation thyroiditis after 131I treatment
  4. Amiodarone (may also be subacute or chronic)
  1. Subacute
  1. Viral (or granulomatous) thyroiditis
  2. Silent thyroiditis (including postpartum thyroiditis)
  3. Mycobacterial infection
  1. Chronic
  1. Autoimmunity: focal thyroiditis, Hashimoto's thyroiditis, atrophic thyroiditis
  2. Riedel's thyroiditis
  3. Parasitic thyroiditis: echinococcosis, strongyloidiasis, cysticercosis
  4. Traumatic: after palpation

Goitrous Hypothyroid

  1. Hashimoto thyroiditis
    1. Most common auto immune cause of goitrous hypothyroidism. It is painless.
    2. Initially patient may be thyrotoxic because hormone due to thyroiditis ↑ permeability, and ↑ leakage of performed but ultimately patient become hypothyroid
    3. 20-60 yrs old women
    4. Histology: Hurthle cells (cells with intensely eosinophilic, granular cytoplasm) are seen, diffuse parenchymal infiltration by lymphocytes.
    5. Anti thyroglobulin antibody and Thyroid peroxidase antibodies are present in the serum.
    6. Antinuclear factor (ANF) may be positive.
    7. Treatment :
      1. Thyroxine therapy
      2. Tamoxifen it ↓ Fibroblast proliferation So ↓ progression of diseases 


  1. It is a type of Hashimoto thyroiditis in which, patient is thyrotoxicosis but her RAIU is reduced.
  2. Hashimoto's encephalopathy has been defined as a steroid-responsive syndrome associated with TPO antibodies, myoclonus, and slow-wave activity on electroencephalography.
  3. Thyroid-associated ophthalmopathy, which usually occurs in Graves' disease, occurs in about 5% of patients with autoimmune hypothyroidism (Ref. Hari. 18th ed.,  Pg - 2920)
  4. Dermopathy is not seen
  5. Associated conditions which can be there = Vitiligo, Addison, Pernicious anemia, type 1 DM 
Extra Edge:

Causes of thyrotoxicosis with  RAIU (Ref. Hari. 18th ed., pg -  2927)

  1. Thyrotoxicosis factitia               
  2. Hashi thyrotoxicosis                      
  3. Struma ovari                       
  4. Excess iodine ingestion              
  5. Functional Metastatic follicular Ca  
  6. Amiodarone therapy    
  7. DE Quervain thyroiditis
  1. Subacute Granulomatous Thyroiditis
    (De Quervain’s thyroiditis, granulomatous thyroiditis or viral thyroiditis).

Clinical manifestations:

  1. Painful and enlarged thyroid, fever (Ref. Hari. 18th ed., pg - 2928)
  2. There may be features of thyrotoxicosis or hypothyroidism, depending on the phase of the illness. 

Laboratory evaluation              

  1. High ESR
  2. Low radioiodine uptake.
  3. TLC may be increased
  4. Thyroid antibodies are negative.


  1. Analgesic
  2. Usually it regresses spontaneously

DD of pain in thyroid gland (Ref. Hari. 18th ed., pg - 2927) 

  1. Acute thyroiditis
  2. Subacute or, rarely, chronic thyroiditis; 
  3. Hemorrhage into a cyst;
  4. Malignancy including lymphoma;
  5. Rarely, amiodarone-induced thyroiditis or amyloidosis.
  1. Riedel’s thyroiditis – (Silent Thyroiditis ) (Ref. Hari. 18th ed., pg - 2929) 
    1. Middle-aged women.
    2. Insidious, painless goiter
    3. Local symptoms due to compression of the esophagus (dysphagia), trachea (stridor), neck veins, or recurrent laryngeal nerves.
    4. Dense idiopathic cause of fibrosis and fibroblast proliferate in thyroid tissue fibrosis disrupts normal gland architecture and can extend outside the thyroid capsule.
    5. Despite these extensive histologic changes, thyroid dysfunction is uncommon. 
    6. The goiter is hard, non tender, often asymmetric, fixed, leading to suspicious of a usually euthyroid malignancy.
    7. Diagnosis requires open biopsy as FNA biopsy is usually inadequate.
    8. Treatment is directed to surgical relief of compressive symptoms.
    9. Tamoxifen may also be beneficial. 

Multifocal fibrosing syndrome fibrosis all over body

  1. Palms = Dupuytren contracture                
  2. Perris Peyronie’s disease
  3. Retroperitoneal Ormond’s disease                    
  4. Mediastinal
  5. Riedel 

4. Drug & causing hypothyroidism

  1. Lithium carbonate
  2. IF-alpha
  3. IL – 2 (Ref. Hari. 18th ed., pg - 2929)
  4. Amiodarone

Amiodarone and Thyroid Gland

Amiodarone and Thyroid Gland (Ref. Hari. 18th ed. , pg -2930)
  1. Due to the high iodine content of the Amiodarone (37.3% by weight), abnormalities in thyroid function are common.
  2. Amiodarone is structurally similar to thyroxine , which contributes to the effects of amiodarone on thyroid function.
  3. Thus, typical doses of amiodarone (200 mg/d) are associated with very high iodine intake, leading to greater than forty fold increases in plasma and urinary iodine levels.
  4. Amiodarone is stored in adipose tissue, high iodine levels persist for >6 months after discontinuation of the drug.
  5. Amiodarone inhibits deiodinase activity, and its metabolites function as weak antagonists of thyroid hormone action.
  6. Both under- and overactivity of the thyroid may occur on amiodarone treatment.
    1. Hypothyroidism (slowing of the thyroid, due to the Wolff-Chaikoff effect) can also occur.
    2. Hyperthyroidism (an overactive thyroid, due to the Jod-Basedow Effect) can also occur. 
  1. Iodine deficiency
    Thyroid enlargement (diffuse goiter) is most common presentation (more than 10% of the population and is known as endemic goitre. Most patients are euthyroid and have normal or raised TSH levels.
  2. Dyshormonogenesis
    The combination of dyshormonogenetic goitre and sensorineural deafness is known as PENDRED’S SYNDROME.

Table. Causes of Congenital Hypothyroidism.
  1. Maternal iodine deficiency                                                           
  2. Fetal thyroid dysgenesis
  3. Inborn errors of thyroid hormone synthesis                              
  4. Maternal antithyroid antibodies that cross the placenta
  5. Fetal hypopituitary hypothyroidism

Special Problems

  1. Hypothyroidism in pregnancy
    1. Most pregnant women with primary hypothyroidism require an increase in the dose of thyroxine of some 50 μg daily.
    2. Explanation for this phenomenon is increase in serum thyroxine-binding globulin concentration during pregnancy, resulting in a decrease in serum free thyroid hormone concentrations which cannot be compensated for by thyroidal secretion.
  2. Hypothyroid and CAD (AIPG 2011)
    In the elderly, especially patients with known coronary artery disease, the starting dose of levothyroxine should be the lowest starting dose i.e. 12.5–25 g/d with similar increments every 2–3 months until TSH is normalized.  (Ref. Hari. 18th ed., pg -  2922) Reason for this is – in hypothyroidism the metabolic rate is low. So myocardial oxygen demand is low.  With sudden treatment with high doses, heart rate will increase and that will lead to coronaryischemia
  3. Myxoedema coma
    1. Depressed level of consciousness, usually in an elderly patient who appears myxedematous.
    2. Body temperature may be as low as 25oC,
    3. Convulsions are common
    4. CSF pressure and protein content are raised.   

Factors contributing to the altered consciousness level,

  1. Cardiac failure          
  2. Chest infection                      
  3. Dilutional hyponatremia
  4. Hypoxemia              
  5. Hypercapnia due to hypoventilation.   

Rx: Myxoedema coma is a medical emergency

  1. I/V Hydrocortisone (1st to be given)        
  2. Parenteral
  3. Slow rewarming.                              
  4. Broad-spectrum antibiotics    
  5. High-flow oxygen.

Test Your Skills Now!
Take a Quiz now
Reviewer Name