Difference Between Hypothyroidism and Hyperthyroidism

Main Difference – Hypothyroidism vs Hyperthyroidism

Hypothyroidism and Hyperthyroidism are two medical conditions which are caused by a problem in the Thyroid gland. The thyroid gland is a small, butterfly-shaped gland, helps in secreting the thyroid hormones (tetraiodothyronine (T4) and triiodothyronine (T3)), and responsible for regulating growth and development through the regulation of the rate of metabolism. The main difference between Hypothyroidism And Hyperthyroidism is the production of thyroid hormones. Hypothyroidism is caused by a lack of thyroid hormones (hypo-metabolic state) whereas Hyperthyroidism is caused by an excess of thyroid hormones (hypermetabolic state). It is very important to know the difference between these two conditions since they have an increased prevalence in the modern society.

In this article, we will focus on,

1. What is Hypothyroidism? – Causes, Signs and Symptoms, Diagnosis and Management

2. What is Hyperthyroidism? – Causes, Signs and Symptoms, Diagnosis and Management

3. What is the difference between Hypothyroidism And Hyperthyroidism?

What is Hypothyroidism

Hypothyroidism is a common endocrine disorder, occurring as a result of thyroid hormone deficiency and can be categorized into primary, secondary and tertiary depending on the basic pathophysiology.

Primary hypothyroidism occurs as a result of an insufficient production of thyroid hormones whereas the secondary hypothyroidism refers to a condition where the thyroid gland itself is normal but receives insufficient stimulation as a result of a low secretion of Thyrotropin (thyroid-stimulating hormone [TSH]) from the pituitary gland. In tertiary hypothyroidism, there is an inadequate secretion of a thyrotropin-releasing hormone (TRH) from the hypothalamus, leading to an insufficient release of TSH which results in an inadequate thyroid stimulation.

An increased incidence of the condition is noted in women with a small body size at birth and low body mass index during childhood.

Major causes of hypothyroidism include inadequate intake of iodine, autoimmune thyroid disease or Hashimoto disease, drugs or idiopathic.

Congenital hypothyroidism is another sup-type of this condition; this affects 1 of every 4000 newborns, potentially due to a congenital maldevelopment of the thyroid gland in the newborn. Furthermore, Cretinism, which refers to severe hypothyroidism in an infant or child, usually occurs as a result of maternal iodine deficiency but fall into a rare group of disorders due to increased health care facilities during pregnancy.

As far as the signs and symptoms of Hypothyroidism are concerned, most of the affected patients will experience slowed-down physical and mental activity, and some can also be asymptomatic, depending on the severity. Also, most of these features are not specific, so it is important to give special attention to one or more disrupting features in order to halt unnecessary negative consequences.

Signs and Symptoms

Fatigue, lethargy, and inactivity
Weight gain despite decreased appetite
Unusual cold intolerance
Dry skin
Hair loss
Excessive laziness and sleepiness
Muscle or joint pain with or without weakness in the extremities
Depression or low mood
Emotional liability
Mental impairment
Forgetfulness and impaired memory, difficulty in concentrating
Constipation
Menstrual disturbances impaired fertility
Reduced perspiration
Paresthesia and nerve entrapment syndromes
Blurred vision
Impaired hearing
Fullness in the throat
Hoarseness of the voice

In addition, patients with Hashimoto’s thyroiditis will characteristically experience a sensation of fullness in the throat, painless enlargement of the thyroid gland, indescribable exhaustion and transient neck pain, sore throat, or both.

Diagnosis of Hypothyroidism mainly includes a complete history of the signs and symptoms, a thorough physical examination, and various laboratory investigations and imaging techniques.

In addition to symptoms mentioned above, there will be important signs observed during the physical examination which mainly include, weight gain, slowed speech and movements, dry skin, jaundice, pallor, coarse, brittle, straw-like hair, loss of scalp hair, axillary hair, pubic hair, or both, full facial expression, coarse facial features, periorbital puffiness, Macroglossia, decreased systolic blood pressure and increased diastolic blood pressure, bradycardia, pericardial effusion, pitting edema of lower extremities and hyporeflexia with delayed relaxation, ataxia, or both.

Laboratory Investigations

Third-generation thyroid-stimulating hormone (TSH) assays- most sensitive screening method for primary hypothyroidism—- ELEVATED
Free thyroxine (T4) or the free thyroxine index (FTI)- DECREASED

Important:

Routine measurement of Triiodothyronine (T3) is not recommended. Elevated TSH and normal free T4 or FTI is considered mild or subclinical hypothyroidism.

Management

Monotherapy with levothyroxine (LT4) is the treatment of choice for hypothyroidism. In fact, exogenous thyroid hormone is administered in order to replace or increase the endogenous production as a single daily dose.
Compliance is highly important for a proper improvement of symptoms.
Annual clinical evaluations and TSH monitoring following the dose stabilization depending on the age of the patient and severity of the condition.

Improperly managed hypothyroidism can lead to the progression of disease and worsening of symptoms with further metabolic abnormalities resulting in profound coma and death. Moreover, untreated hypothyroidism in infants can give rise to irreversible mental retardation.

What is Hypothyroidism

Hyperthyroidism is a condition which occurs as a result of increased production of thyroid hormones (T4, T3, or both) from the thyroid gland.

Graves’ disease is an autoimmune disorder which accounts for most of the cases of hyperthyroidism. Thyroiditis or inflammation of the thyroid, ovarian or testicular tumors, benign or malignant tumors of the thyroid gland and large amounts of tetraiodothyronine through dietary supplements are also known to play a major role in giving rise to the condition.

High amounts of T4/ T3/ both can result in an excessively high metabolic rate also known as a hypermetabolic state where the patients will experience increased heart rate, increased perspiration, elevated blood pressure, tremors, diarrhea, weight loss despite of increased appetite, difficulty in sleeping, trouble in concentrating, restlessness, hair loss, weakness, heat intolerance and irregular menstrual cycles in women.

Some patients will have a visible enlargement of the thyroid gland which can spontaneously develop into a goiter, either symmetrical unilateral. There can also be a protrusion or bulging of the eyes resulting in a ‘staring look’ which is known as exophthalmos, a sign of Graves’ disease.

Undiagnosed Hyperthyroidism can result in a fatal arrhythmia known as atrial fibrillation which can lead towards a stroke or congestive heart failure.

The diagnosis of hyperthyroidism will mainly be made by taking physical examinations, biochemical alterations identified with laboratory investigations such as TSH levels, T3 and T4 levels. In fact, an abnormally low TSH might be the first sign of hyperthyroidism.

Furthermore, Thyroid re-uptake test and thyroid scan will help to identify a completely or partially over-reactive thyroid gland. Also, Ultrasound scan of the thyroid gland will help to assess the size of the gland and to determine whether the mass is solid or cystic which can mark the cause for the enlargement to occur. A CT or MRI scan will support if the diagnosis is more towards a pituitary tumor which can also result in hyperthyroidism in an indirect way.

Management

Anti-thyroid medications (Carbimazole, Methimazole)
Radioactive iodine, which destroys cells which produce an undue amount of hormones
Surgery- complete or partial removal of the gland in cases which do not respond to medical treatments. It is important to have thyroid hormones supplements after the surgery to prevent hypothyroidism.
Beta-blockers (Propranolol) are used to improve symptoms related to hypermetabolic state (anxiety, rapid heart rate)
Vitamin D supplements

The main outlook of Hyperthyroidism mainly depends on the primary etiology. Some causes can disappear with proper medications while underlying conditions like Grave’s disease can result in various negative consequences and can even be life-threatening if left untreated.

Enlarged thyroid that may be associated with hyperthyroidism

Production of Thyroid Hormones

The major difference between Hypothyroidism And Hyperthyroidism is the output of thyroid hormones. In fact, Hypothyroidism accounts for a thyroid gland which doesn’t produce enough amount of hormones (hypo-metabolic state), meeting the requirements of the body whereas Hyperthyroidism occurs as a result of an over-reactive thyroid gland (hypermetabolic state).

Causes

The commonest cause of hypothyroidism is an autoimmune disease named as Hashimoto’s disease where Grave’s disease marks the highest incidence in diagnosed hyperthyroid cases.

Signs and Symptoms

Moreover, patients with Hypothyroidism will experience signs and symptoms related to a slow metabolism of the body whereas those with Hyperthyroidism will have ones related to an increased metabolism.

Special differences

An increased weight despite a poor appetite is a characteristic feature of Hypothyroidism while the loss of weight despite an increased appetite is a characteristic feature of Hyperthyroidism.
Cold intolerance is unique to Hypothyroidism whereas heat intolerance is seen only in patients with hyperthyroidism.

Diagnosis

As far as the diagnostic investigations are considered, biochemical markers such as TSH, T3, and T4 levels will also give a different result which will differentiate these two conditions. In fact, TSH levels will be elevated in Hypothyroidism whereas it can either be normal or reduced in the latter. T3 and T4 levels will be reduced in Hypothyroidism whereas they will be slightly elevated in Hyperthyroidism.

Treatment

Levothyroxine marks the hallmark therapy for Hypothyroidism and Hyperthyroidism can be treated either with pharmaceutical agents such as Carbamazepine which is an anti-thyroid drug, radiotherapy or surgical removal of the thyroid gland, depending on the severity or response to each treatment method.

Image Courtesy:

“Signs and symptoms of hypothyroidism” Häggström, Mikael. “Medical gallery of Mikael Häggström 2014”. Wikiversity Journal of Medicine 1 (2). DOI:10.15347/wjm/2014.008. ISSN 20018762. – Own work (CC0) via Commons Wikimedia

“Blausen 0534 Goiter” By Blausen.com staff. “Blausen gallery 2014”. Wikiversity Journal of Medicine. DOI:10.15347/wjm/2014.010. ISSN 20018762. – Own work, (CC BY 3.0) via Commons Wikimedia