Hypothyroidism

Hypothyroidism is a common disorder characterized by inability of the thyroid gland to produce sufficient thyroid hormones in the bloodstream. Since thyroid hormones play a vital role in metabolism and energy production, their deficiency may affect digestion, breathing, heart rate, mood and weight. 

Symptoms of Hypothyroidism:

The signs and symptoms depends on the severity of the condition and include:

1. Fatigue
2. Weight gain
3. Depression
4. Constipation
5. Feeling cold
6. High cholesterol level
7. Dry skin
8. Impaired memory
9. Muscle weakness and tenderness
10. Slow Heart rate
11. Joint pain 

Mechanism of the thyroid gland:

The thyroid gland is a small, butter-fly organ located in the front of the neck under the larynx and plays a major role in metabolism, growth and development of our body by secreting the thyroid hormones triiodothyronine (T3) and tetraiodothyronine (T4) into the bloodstream. One of the main building blocks of the thyroid hormones is iodine which is absorbed from food to the bowel and then carried to the thyroid gland to be used for production of thyroid hormones.

The Thyroid gland is controlled by another gland called, the pituitary gland, a small gland located at the bottom of the brain. The pituitary gland produces the thyroid-stimulating hormone (TSH) which signals the thyroid gland to secrete thyroid hormones. TSH levels are rising or falling according to our body’s needs for the thyroid hormones. Also, the thyroid hormones are attached in the bloodstream to transport proteins and to function properly, the thyroid hormones must be released from these proteins in the free forms, freeT3 and free T4. 

Normally, the thyroid gland secretes the exact amount of thyroid hormones needed to balance the metabolism of our body. However, certain disorders may cause the thyroid gland to produce  more thyroid hormones (Hyperthyroidism) or insufficient thyroid hormones (Hypothyroidism), resulting in faster or slower metabolic rate.

Causes :

The causes of hypothyroidism are divided into primary and secondary causes. The primary causes are the most common and results from inability of the thyroid gland to secrete sufficient amounts of thyroid hormones. However, the secondary causes results from failure of the pituitary gland to secrete TSH to balance out the thyroid hormones. Also, the major causes of  include:

1. 1. Hashimoto’s disease:
      It’s an autoimmune disease and the most common cause of hypothyroidism. With this disease, the immune system attacks the thyroid gland causing its inflammation and its inability to produce enough thyroid hormones.
   2. Thyroiditis:
      It is caused by inflammation of the thyroid gland and leakage out of the thyroid hormones into the bloodstream. This condition may last several months until the thyroid gland becomes underactive .
   3. Congenital Hypothyroidism:
      Few babies are born without a fully functional thyroid gland or thyroid gland that doesn’t function properly. If this condition is left untreated, it can cause growth failure and mental disability.
   4. Surgery:
      Some people with hyperthyroidism, Grave’s disease, thyroid nodules, or thyroid cancers undergo surgical removal of part or all the thyroid gland and develop hypothyroidism. 
   5. Radiation Treatment:
      The most common treatment for hyperthyroidism is radioactive iodine which may gradually destroy the thyroid gland leading to hypothyroidism. Also radiation therapy used for people with head and neck cancers may destroy the thyroid gland.
   6. Medicines:
      Some medicines, particularly used for treatment of cancers, heart disorders, and bipolar disorders, may affect the production of thyroid hormones.
   7. Damage to the pituitary gland:
      The pituitary gland may be damaged due to radiation, surgery, or tumor and stops signaling the thyroid gland to secrete thyroid hormones.
   8. Iodine deficiency:
       Iodine is a trace element essential for thyroid hormone production. It is obtained from seafood, seaweed, eggs and some plants and its deficiency may result in hypothyroidism. 
   9. Pregnancy:
       About 5 – 10% of pregnant women may develop thyroiditis during or after pregnancy which may lead to hypothyroidism. 

Risk factors: 

Several factors may increase the risk which include:

1. Sex: being female
2. Age: being older than 60 years old
3. Family history: having family history of hashimoto’s disease or other autoimmune disorders
4. Autoimmune disease: the risk increases in patients with diabetes type I, rheumatoid arthritis or other autoimmune diseases
5. Pregnancy or postpartum
6. Insufficient iodine consumption
7. Thyroid surgery: removal of all or part of the thyroid gland.
8. Radioactive iodine or anti-thyroid therapy for treatment of hyperthyroidism or thyroid cancers.
9. Radiation therapy to the neck or upper chest 
10. Some medications: like lithium used for bipolar disorders, heart disorder medications, and cancer medications. 

Complications:

If hypothyroidism is left untreated, it may cause several complications. Being aware of the symptoms and early diagnosis may prevent these complications which include:

1. Cardiovascular Problems:
   Hypothyroidism may affect heart health as it increases LDL-cholesterol which contributes to high cholesterol level and may cause atherosclerosis and increases the risk of heart attack and strokes.
2. Goiter:
   When the thyroid gland becomes underactive, it exerts effort to secrete thyroid hormones and this may cause enlargement of the thyroid gland with the formation of  a bulge in the neck which is called Goiter.
3. Birth Defects:
   If a pregnant woman has hypothyroidism and is left untreated, the child may have mental and physical defects as thyroid hormones are essential for brain development.
4. Mental Health Issues:
   Hypothyroidism may cause mild depression and anxiety and without treatment, the condition may be intensified and cause gradual decrease in the mental ability. 
5. Pregnancy complications:
   Hypothyroidism during pregnancy may increase the risk of miscarriage, preeclampsia, or preterm birth.
6. Infertility:
   Hypothyroidism may cause infertility in both men and women as thyroid hormones regulate sex hormone metabolism. Women with hypothyroidism are more likely to have menstrual problems.
7. Nervous system problems:
   Hypothyroidism may cause nerve damage and muscle weakness which may result in tingling, numbness and severe pain in the affected areas. 
8.  Myxedema (Coma):
   It’s a rare and life-threatening condition caused by long-term untreated hypothyroidism and extremely low levels of the thyroid hormones. It is characterized by lethargy, hypothermia, and drowsiness and may lead to loss of consciousness.

Diagnosis of Hypothyroidism:

The symptoms of hypothyroidism may interfere with other conditions, however there are many tests to diagnose hypothyroidism. Blood tests are the most identified tests and include:

1. TSH : It is the primary test to diagnose thyroid problems. TSH is secreted from the pituitary gland to regulate the secretion of thyroid hormones T3 and T4 from the thyroid gland. Imbalance of thyroid hormones in our blood stream mostly affects TSH level.
2. T3: Triiodothyronine: it helps to diagnose hypothyroidism or hyperthyroidism. 
3. T4: Thyroxine: It can be used to diagnose hypothyroidism or hyperthyroidism and to monitor treatment of thyroid disorders.
4. FT3: Free T3 or free triiodothyronine: It measures the free form of T3 to eliminate the effect of proteins binding to T3.
5. FT4: Free T4 or free thyroxine: It measures the free form of T4 to eliminate the effect of proteins binding to T4.
6. Thyroid antibodies: They help to identify autoimmune thyroid disorders and include:
   Anti thyroid peroxidase antibody (Anti-TPO)
   Anti thyroglobulin Ab
   Anti TSH receptor antibody.
7. Thyroglobulin: It is used for the diagnosis of thyroiditis and to monitor thyroid cancer.

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