Hypothyroidism is the reduced activity of the thyroid gland (underactive thyroid) leading to a decrease in circulating thyroid hormones. This slows the metabolic activity within the body.

Hyperthyroidism (thyrotoxicosis) is the increased activity of the thyroid gland (overactive thyroid) resulting in an increase in the level of thyroid hormones circulating in the blood. This speeds up the metabolic activity within the body.

There are many causes of both hypo- and hyperthyroidism but the most common cause in both instances are autoimmune diseases – Hashimoto’s thyroiditis (hypothyroidism) and Grave’s disease (hyperthyroidism).

Signs and Symptoms of Underactive and Overactive Thyroid

The signs and symptoms of both conditions are related to the excess or deficiency of circulating thyroid hormones. Some of the signs and symptoms may overlap – goiter (enlarged thyroid gland) may be present in both hypo- and hyperthyroidism depending on the cause. The clinical feature of both conditions may also depend on the severity and period of time for which the condition was persisting.

There are other signs and symptoms of both hypo- and hyperthyroidism that may not be mentioned in this article. The table below lists signs and symptoms that will allow a person to identify the differences between each condition in the event of a thyroid dysfunction. Serious complications of both hypo- and hyperthyroidism may appear as other conditions (discussed below).

Sign / SymptomHypothyroidismHyperthyroidism
BODY WEIGHTWeight gain.Weight loss.
TEMPERATURE SENSITIVITYCold intoleranceHeat intolerance
HEART RATEBradycardia. Slow heart rate (low pulse).Tachycardia. Fast heart rate (high pulse)
BLOOD PRESSUREHypertension/hypotension. Diastolic pressure high while systolic pressure may be low.Hypertension.
SEXUAL/REPRODUCTIVE FUNCTIONINGInfertility.
Loss of libido.
Erectile dysfunction.
Infertility.
Loss of libido.
Erectile dysfunction.
Spontaneous abortion.
ENERGY LEVELSFatigue. Slow and sluggish. Sleepiness.Fatigue but hyperactive. Cannot sit still.
BOWEL MOVEMENTSConstipation.Diarrhea.
MENTAL STATE
Depression.
Poor memory.
Inability to concentrate.
Anxious.
Irritable.
Nervousness.
FLUID ACCUMULATIONLeg, hands, eyelid swelling* (non-pitting edema although pitting edema may be present in lower limbs).
Fluid around the lungs (pleural effusion) and heart (pericardial effusion).
Abdominal swelling.
Round, puffy face.
Ankle swelling.
Feet and toes may also be swollen.* Protruding eyeballs (exopthalmos) with lid retraction may be present and is not the same as puffy eyelids as in hypothyroidism.
SKIN & HAIRDry, pale skin.
Dry, coarse hair.
Purple-tinged lips.
Itchy skin.
Hair loss.
Loss of lateral eyebrows.
Red rash with lines of hyperpigmentation.
Perspiration (sweaty skin) – moist to touch.
Warm and smooth feel of the skin.
Thinning of the skin.
Pigmentation.
Itchy skin.
Hair loss.
Redness of the palms.
REFLEXESDelayed relaxation of reflexes.Overactive reflexes (hyperreflexia).
MENSES (women)Heavy flow.
Prolonged or frequent periods.
Lighter flow.
Absent or infrequent periods.
MUSCLES/MOVEMENTSMuscle stiffness. Slow relaxation of muscles. Aches and pains.Tremors – shaky hands. Muscle weakness.

Signs of Serious Complications

Elderly patients are more likely to experience serious complications related to hypothyroidism or hyperthyroidism and the signs and symptoms of these conditions may be mistaken for other life-threatening conditions. Younger patients may also experience these complications in severe cases.

  • Hypothyroidism : Myxedema coma presents with a decreased level of consciousness. Body temperature may be low, convulsions sometimes present, and increased intracranial pressure.
  • Hyperthyroidism : Thyrotoxicosis crisis (thyroid storm) presents as a very agitated and confused patient with a fever. Heart rate is increased (tachycardia) and irregular (arrhythmia) and there are signs of heart failure.

Related Articles

  1. Symptoms of Hypothyroidism
  2. Hashimoto’s Thyroiditis
  3. Low Thyroid Test Levels

Article reviewed by Dr. Greg. Last updated on June 17, 2010