The thyroid is one of the most important body parts, as it is responsible for maintaining many vital body functions such as heart rate, managing the digestive system, etc. The term hypo means low, and hence the name hypothyroidism or underactive thyroid indicates low thyroid level in the body. Though women are more affected by this condition, it is one of the common conditions among people over 60 years of age. Hypothyroidism is not a serious health condition and can be easily treated with proper medical treatment.

What Causes Hypothyroidism?

There are several causes of hypothyroidism, and it can be due to either,

Primary thyroid gland disorders (primary hypothyroidism).
Decreased TSH (thyroid-stimulating hormone) secretion by the pituitary gland (secondary hypothyroidism).
Post-surgeries like thyroidectomy for hyperthyroidism or large goiter.
Post-ablative causes (radio-iodine therapy for hyperthyroidism).

A. Primary Hypothyroidism:

1. Removal of some or all parts of the thyroid gland.

2. Following iodine 131 administration for hyperthyroidism.

3. Congenital hypothyroidism.

4. Goitrous.

Hashimoto's thyroiditis - Immune system attacks the thyroid, which is the most common cause.
Iodine deficiency.
Drug-induced such as lithium, amiodarone, and methimazole.
Genetic enzyme defects (dys-hormonogenesis).
Inflammation of the thyroid.

B. Secondary Hypothyroidism:

1. Destruction of the pituitary gland,

After surgery.
Radiation treatment.
Tumor.

2. Disorders of the hypothalamus.

The common cause of hypothyroidism worldwide is iodine deficiency. However, hypothyroidism might occur in areas where iodine deficiency is absent, known as autoimmune thyroiditis. Autoimmune hypothyroidism is initially associated with goiter (Hashimoto's thyroiditis). Later it becomes atrophic, namely atrophic thyroiditis (organ-specific autoimmune disease).

Who Is at Risk for Hypothyroidism?

The risk of getting hypothyroidism is greater in,

Women - Particularly older women are more prone to get hypothyroidism than men.
People whose close relatives have hypothyroidism or autoimmune disease.

The other risk factors are seen in people with:

Type 1 diabetes.
Have had surgery for a thyroid problem.
Turners syndrome.
Autoimmune disorders such as multiple sclerosis, celiac disease, rheumatoid arthritis, Addison's disease, vitiligo, or pernicious anemia.
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Radiation treatment to the thyroid, chest, or neck.
Pregnant or became a mother recently.
Lupus (a chronic autoimmune disease).

What Are the Clinical Manifestations of Hypothyroidism?

1) In Adults:

The signs and symptoms vary from person to person, and the important symptoms of hypothyroidism in adults are,

General symptoms:

Weakness.
Cold intolerance.
Hair loss.
Tiredness.
Dry, coarse skin.
Loss of color of the skin and mucous membrane.
Puffy face, hand, and feet.
Goiter (swelling of the thyroid gland).
Myxedema (a severe form of hypothyroidism).
Poor appetite.
Weight gain.
Hypothermia (faster loss of body heat).
Hoarse voice.

Gastrointestinal symptoms:

Constipation.
Enlarged tongue.
Bloating.

Reproductive symptoms:

Menorrhagia (abnormal menstrual bleeding).
Amenorrhea (absence of menstrual bleeding).
Infertility.
Galactorrhea (milky nipple discharge).

Nervous system symptoms.

Poor memory.
Poor concentration.
Numbness.
Tingling.
Delayed relaxation of deep reflexes.
Weakness of hands.

Cardiovascular symptoms:

Bradycardia (slower than normal heartbeat).
Hypertension.
Ischemic heart disease (damage to major blood vessels of the heart).
Pericardial effusion (extra fluid in the space around the heart).

Prolonged hypothyroidism causes the deposition of hydrophilic mucopolysaccharides in tissues. This results in non-pitting edema (myxedema). As hypothyroidism develops slowly, many people will not be able to notice the signs and symptoms of the disease for several months or years.

2) In Infants or Babies:

Infants with hypothyroidism will not have any symptoms. However, if symptoms occur, they may show up the following.

Little or no growth.
Constipation.
Poor feeding habits.
Extreme sleepiness.
Hoarse cry.
Stomach bloating.
Cold hands and feet.
Low muscle tone.
Persistent jaundice (yellowish discoloration of the skin and whites of the eyes).
Puffy face.
Umbilical hernia (an abnormal opening makes the organ or the tissue bulge).
Swollen tongue.

3) In Children and Teens:

They might also have hypothyroidism with symptoms seen in adults. In addition, they also have:

Delayed growth.
Delay in puberty.
Slower mental development.
Delayed eruption of permanent teeth.

What Are the Complications of Hypothyroidism?

If hypothyroidism is untreated, it might lead to various complications such as:

Increasing the risk for heart problems.
Contributes to high cholesterol.
Leading to myxedema coma, a condition where the body's functions slow down to a point, resulting in a life-threatening condition.
Increased body weight.
Joint pain.
Pregnancy complications such as miscarriage, high blood pressure in pregnancy, and premature birth. In addition, it slows down the growth and development of the baby.

How Is Hypothyroidism Diagnosed?

If the patient experiences the symptoms of hypothyroidism, the doctor will ask for the following to confirm the diagnosis.

Family history of hypothyroidism.
Past and present medical history.
Physical examination.
Thyroid Function Tests: High serum TSH (thyroid-stimulating hormone) is the earliest indicator of primary hypothyroidism, and when it is low, it indicates secondary hypothyroidism. The serum T4 (thyroxine) is low in hypothyroidism. High serum thyroid-stimulating hormone and normal serum thyroxine might indicate subclinical or mild hypothyroidism, which is the early stage of hypothyroidism. High titer antibodies against thyroglobulin and thyroid peroxidase (TPO) are found in patients with Hashimoto's thyroiditis and atrophic thyroiditis.

Blood Tests: The blood reports of people with hypothyroidism show,

Anemia (normocytic or macrocytic).
Increased serum creatine kinase.
High serum cholesterol.
Increased triglycerides.
Elevated LDH (lactate dehydrogenase).
Decreased sodium levels in the blood.

If the doctor suspects hypothyroidism with the above diagnosis, then further diagnosis with the imaging tests is taken to check for the nodules or inflammation.

Thyroid scan.
Ultrasound.

How Is Hypothyroidism Treated?

Hypothyroidism should be treated with oral Levothyroxine. The treatment is usually started with a low dose (50 to 100 micrograms daily) and gradually increases. In elderly individuals, a smaller starting dose (25 micrograms) is preferred to avoid cardiac side effects. Thyroid-stimulating hormone is monitored periodically, and the dosage adjustment of thyroxine is made accordingly. The ideal goal is to maintain thyroid-stimulating hormone at the lower half of the reference range, and the treatment is needed lifelong.

Conclusion:

As a person gets older, it is natural for some changes to occur in our body, such as the low production of thyroid hormones. This is very common and can be easily managed with proper medical treatment and a balanced diet. Since there might be other conditions associated with hypothyroidism, it is necessary to consult a doctor regularly to keep track of the treatment progress.