Hypothyroidism | Causes | Clinical features and Diagnosis for Thyroid Gland Disorders

What is Hypothyroidism

Disorders of thyroid glands are classified into 2 categories

1. Hyperthyroidism- due to excessive secretion
2. Hypothyroidism- due to deficient secretion

Hypothyroidism is due to suboptimal circulating levels of one or both T3 and T4.

Causes of Hypothyroidism

Common causes of hypothyroidism are

1. Auto-immune thyroiditis.
2. Hashimoto’s disease. In 1 and 2 there is progressive destruction of thyroid tissue. Circulating antibodies are present in high concentration.
3. Other inflammatory diseases of the gland.
4. Following treatment of hyperthyroidism-

• Post-thyroidectomy.
• Post 131-iodine therapy.
• Idiopathic hypothyroidism.

Rare causes are exogenous goiter, drugs (including lithium) and dyshormonogenesis.
Main difference between primary and secondary forms of hypothyroidism is in levels of plasma TSH – high TSH level occurs in primary and low TSH occurs in secondary hypothyroidism.

Clinical features of Hypothyroidism

1. General- tiredness, somnolence, weight gain, cold intolerance and goiter.
2. Skin and subcutaneous tissues- coarse dry skin, puffiness of face, baggy eyelids, minimal sweating, alopecia and vitiligo (white discoloration).
3. Myxedema- swollen edematous appearance of supra-clavicular regions, neck, back of hand and feet.
4. Cardiovascular and respiratory- bradycardia (slow heart rate- below 60 beats), angina, cardiac failure with pericardial effusion and pleural effusion.
5. Psychiatric features- depression and myxo-edema madness.
6. Neuro-muscular- aches and pains, carpel tunnel syndrome, slurred speech and ataxia with muscle cramps and stiffness. Hoarseness of voice.
7. Gastrointestinal- constipation and ascites.
8. Hematological- anemia (iron deficiency), vitamin B12 deficiency and pernicious anemia,
9. Reproductive system- infertility, menorrhagia and impotence.
10. Development- growth retardation, mental retardation and delayed puberty.
11. Miscellaneous- impairment of smell, taste and hearing; hoarse husky voice, nails striated and tend to break and decreased tone of muscles.

Hypothyroidism Diagnosis

• Thyroid function test- reduction in free and total T4 and rise in serum TSH indicates primary hypothyroidism. Elevated serum TSH with normal serum T4 is termed ‘sub clinical’ hypothyroidism.
• Serum cholesterol- elevated in primary thyroid failure.
• Tendon reflex duration- tendon reflexes are prolonged.
• Thyroid antibodies- antibodies to thyroglobulin or thyroid peroxidase are typically strongly positive in Hashimoto’s thyroiditis.

Treatment for Hypothyroidism

• Replacement therapy- thyroxin (T4) is the treatment of choice.
• Duration of therapy is usually life long.

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