Hypothyroidism is an endocrine disorder caused by deficiency of Thyroid hormone which results in systemic manifestation of a spectrum of symptoms.
Prevalence : Primary hypothyroidism is 1:100 but increases upto 1:20 if patients with subclinical hypothyroidism are included. But in Mountainous region of Nepal, Iodine deficiency is common.
Etiology or Causes of Hypothyroidism:
Autoimmune or Hashimoto’s Disease and Iatrogenic causes account for maore than 90% of cases.
Mnemonic- “AITI CIS” ( 80 Kiss)
- Autoimmune- Hashimoto’s thyroiditis, Spontaneous Atrophic hypothyroidism,Grave’s Disease with TSH receptor blocking Ab.
- Iatrogenic – Radioactive Iodine Ablation, Thyroidectomy, Drug- Carbimazole, Methimazole, Lithium, Amiodarone
- Transient Thyroiditis- Subacute or de Quervian’s thyroiditis, Post-partum thyroiditis
- Iodine deficiency- common in mountainous region.
- Congenital- Dyshormonogenesis, Thyroid aplasia
- Infiltrative- Amyloidosis, Reidel’s thyroiditis, sarcoidosis.
- Secondary Hypothyroidism- TSH deficiency
Clinical Features :
- Weight gain
- Cold intoerence
- Yellowish tinge of skin ( Carotenemia )
- Fatigue, somnolence
- hoarseness of voice
- Aches and pains
- depression or physosis ( Myxedema madness)
- Dry skin , hair, alopecia
- Menorrhagia, Infertility, Galactorrhea, Impotence
The body tissues are infiltrated by the mucopolysaccharides, hyaluronic acid and chondroitin sulphate resulting in low pitched voice, deafness, large tonge and Carpal tunnel syndromes.
Bradycardia, Hypertension and Pericardial or pleural effusion.
Delayed tendon reflexes
Myxedema, purplish lips, malar flush, Vitiligo, Erythema ab igne
Periorbital edema, loss of eye brows
Non-specific Lab abnormalities seen:
- Serum Enzymes- Raised CK, AST, LDH.
- Anaemis- Normochromic normocytis or macrocytic
Thyroid Function Test-
- Serum free T3, T4 and TSH can determine the type of Hypothyroidism. ( Clinical , Subclinical)
Measurement of Thyroid Peroxidase antibodies is helpful
- Unless its transient Hypothyroidism, patient will require life-long replacement.
- Start with 50 Microgram of Thyroxine per day for 3 weeks
- Increase to 100 microgram per day in next 3 weeks
- Then to Maintainance dose of 100-150 microgram per day
- TFT can be repeateda after 6 weeks. Adjustment dose is increased by 25 microgram.
- Patient feels better in 2-3 weeks.
- Repeat TFT every 1-2 year.
In special conditions :
Ischemic heart disease: low dose of 25 Microgram per day
Pregnancy:- additional 50 microgram is needed.
Reference : Davidson’s Principle and Practice of Medicine.