In this article we will discuss in detail about Hypothyroidism, its causes, clinical features or signs & Symptoms, diagnosis and management as well as treatment of hypothyroidism.
Causes of Hypothyroidism
Hypothyroidism can be of three types depending on source of pathology. Primary Hypothyroidism is a condition when there is something intrinsically wrong with thyroid and it does not produce adequate amount of thyroid hormones like T3 and T4. This one is the most common cause of hypothyroidism and more than 95% of cases of hypothyroidism as of primary in nature.
Primary hypothyroidism can be secondary to many pathological states, most common being Hashimoto Disease which is a kind of chronic hypothyroidism. Hashimoto disease or thyroiditis results in goiter and is associated with anti-microsomal antibodies. The disease will be discussed in detail in subsequent articles.
Other causes include treatment of hyperthyroidism like surgery, radioactive iodine. Iodine deficiency and genetic defects in synthesis of T3 and T4 can lead to primary hypothyroidism as well.
Drug Induced Hypothyroidism: Drugs like lithium, amiodarone, acetylsalicylic acid, interferon and sulfonamides can cause primary hypothyroidism.
Pituitary induced hypothyroidism is also known as secondary hypothyroidism. The blood level of TSH as well as T3 and T4 is decreased unlike primary hypothyroidism in which T3 and T4 is decreased while serum TSH is high.
Pathology is in hypothalamus which is responsible for release of Thyroid Releasing Hormone [TRH]. Decreased level of TRH causes pituitary to release less TSH which results in underproduction of T3 and T4 by thyroid glands resulting in tertiary hypothyroidism.
Signs & Symptoms
Hypothyroidism based on age of the patient can be classified under two major categories. In new born hypothyroid state is also known as cretinism or juvenile hypothyroidism while in adults it is called as adult hypothyroidism
The classical features of cretinism includes following signs & symptoms
- Physiological jaundice
- Horse cry
- Wide set eyes
- Umbilical hernia
- Feeding problems
- Drowsiness and state of sleepiness [Somnolence]
With progression of age the child has coarse facial features, protruding tongue, flat nose, impaired mental development, delayed milestones and dwarfism.
Scanty hair with dry scaly skin is also seen in juvenile hypothyroidism
Signs & Symptoms of Hypothyroidism in adults
Signs and symptoms of adult hypothyroidism include classical history where patient complains of following
- Cold intolerance
- Weight gain
- Muscle cramps
- Decreased appetite
On close examination doctor may illicit following history and signs
- Coarse and deep voice
- Loss of hearing
- Slow deep tendon reflexes [Prolonged relaxation phase]
- Flat and expressionless face, scanty hair, cool skin with large tongue and swelling around the eyes
- High cholesterol, decreased blood sodium levels and anemia might also be associated.
Diagnosis, Investigation & Lab tests
Diagnosis of hypothyroidism is made by physical findings and symptoms. Tests are run to confirm the diagnosis and start the treatment
Blood TSH level is increased while T3 and T4 is decreased in primary hypothyroidism
Blood TSH level is decreased along with T3 & T4 in secondary and tertiary hypothyroidism.
Management and treatment of hypothyroidism is done based on age and other co-morbid conditions. For patients who are older or have coronary artery disease [CAD] the aim is to restore normal metabolic state gradually so that cardiovascular system is not stressed.
Levothyroxine [T4] is given with close monitoring of T3 and TSH. Usually it takes 4-6 weeks before the levels are stabilized and dosage is adjusted accordingly.
In adults the dosage is around 100 micro-grams per day. While in older patients the dosage is kept around 25-75 micro-grams per day of levothyroxine.
If there is suspicion of supra-thyroid cause like secondary and tertiary hypothyroidism it is advisable to give hydrocortisone first then change it to thyroid hormone.