Types, Causes and Management of Hypothyroidism

Definition of Hypothyroidism:

A Clinical condition characterized by subnormal level of circulating thyroid hormones. It associated with generalized non pitting ordema is called myxocdema.

Classification of Hypothyroidism:

1. Primary: Here the abnormality is within thyroid gland, either structural or functional.

2. Secondary: Here the abnormality is in the hypothalamic-pituitary axis resulting in decreased production of TSH.

In another classification:

Goitrous: Associated with enlargement of thyroid gland.

Nongoitrous: Not associated with enlargement of thyroid gland.

Causes of Hypothyroidism:

1. Autoimmune:

• Hashimoto’s thyroiditis,
• Spontaneous atrophic hypothyroidism,
• Graves’ disease with TSH receptor-blocking antibodies.

2. latrogenic :

• Radioactive iodine ablation,
• Thyroidectomy,
• Drugs : Lithium, Carbimazole, methimazole, propylthiouracil , Amiodarone.

3. Transient thyroiditis:

• Subacute (de Quervain’s) thyroiditis,
• Post-partum thyroiditis.

4. Iodine deficiency: e.g. In mountainous regions

5. Congenital:

• Dyshormonogenesis,
• Thyroid aplasia.

6. Infiltrative:

• Amyloidosis,
• Riedel’s thyroiditis,
• Sarcoidosis etc.

7. Secondary hypothyroidism: TSH deficiency

Management of Hypothyroidism:

Clinical feature of Hypothyroidism:

• Fatigue,
• Increased sensitivity to cold,
• Constipation,
• Dry skin,
• Weight gain,
• Puffy face,
• Hoarseness,
• Muscle weakness,
• Elevated blood cholesterol level,
• Muscle aches, tenderness and stiffness,
• Pain, stiffness or swelling in your joints,
• Heavier than normal or irregular menstrual periods,
• Thinning hair,
• Slowed heart rate,
• Depression,
• Impaired memory.

Investigation of Hypothyroidism:

1. Thyroid function tests:

• Total T4 & T3: T4 & T3 – decreased,
• TSH- increased,
• Free T4 & T3 – decreased.

2. Antithyroid antibodies:

• Antimicrosomal /peroxidaseAb,
• Antithyroglobulin ab.

3. Thyroid scan, USG, FNAC.

4. Routine exam: Rx:

• CBC- Anaemia,
• Serum cholesterol & TG : Raised,
• Urine R/M/E,
• X- ray chest : Cardiomegaly,
• ECG (>40 yrs): Low boltage ECG,
• Ischacmia,
• Bradycardia,
• X-ray neck lateral and A/P view V Retrosternal extension,
• Serum Na+ level: – decreased,
• Serum enzymes: Raised AST, CK & LDH.

Rx:

1. Oral thyroxin single dose/day.

Replacement dose:

• 50 ug0.05 mg daily & then increased,
• 1st 3 wks -50 µg once daily,
• 2nd 3 wks – 100 µg once daily,
• Lifelong — 150 µg once daily.

Hypothyroidism with IHD: Start with low dose such as 25 µg day.

2. If rapid response is required, tri-iodothyronine 20 µg 3 times daily.

Follow up:

Regular thyroid function test -6 weekly & adjust thyroxin dose.

Once the dose of thyroxin is established – thyroid function test-1-2 yearly.

Difference Between Hypothyroidism and Hyperthyroidism:

Points of Difference	Hypothyroidism	Hyperthyroidism
About	Also known as over active thyroid.	Also known as underactive thyroid.
Most Common Cause	Graves’ disease, also known as toxic diffuse goiter.	Hashimoto’s disease, also known as chronic lymphocytic thyroiditis.
Other Causes	Thyroiditis, iodine deficiency, medication, thyroid nodules.	Thyroiditis, too much iodine, medication, genetics, hyperthyroidism treatments.
Diagnosis	Thyroid-stimulating hormone (TSH) test, thyroid-stimulating immunoglobulin (TSI) test, thyroid scan, radioactive iodine uptake test.	Thyroid-stimulating hormone (TSH) test, thyroid-stimulating immunoglobulin (TS) test, thyroid scan, radioactive iodine uptake test.
Treatment	Antithyroid medication (e.g., Methimazole) to slow overactive thyroid and, sometimes, beta blockers (e.g., Propranolol) to alleviate symptoms.	Synthetic thyroid hormone (e.g., Levothyroxine) or carefully monitored iodine supplementation.
Occurrence	Less common. Roughly 1%% of U.S. has overactive thyroid. Women more likely to suffer due to effects of pregnancy.	More common. Nearly 5% of U.S. , could be as much as 20% if what is considered “normal” range is slightly adjusted. Women more likely to suffer due to effects of pregnancy.
Appetite	Weight loss but increased appetite.	Weight gain but loss of appetite.
Pulse	Tachycardia	Bradycardia
Skin	Warm and moist	Dry and coarse
Hair	Fine and soft	Thin and brittle
Temperature Intolerance	Heat intolerance	Cold intolerance