Thyroid Hormones
 

The thyroid gland releases two noteworthy hormones:  triiodothyronine (T3), and thyrosine (T4). These hormones are involved in multiple facets of bodily function including regulation of metabolism and growth and development. The synthesis of these two thyroid hormones is regulated by the pituitary gland and its release of thyroid stimulating hormone (TSH) via negative feedback pathways from low levels of T3 and T4.

Increased levels of thyroid hormones stimulate the metabolism of fat and carbohydrates. The action of thyroid hormones affects growth and development of both adults and children. Individuals deficient in thyroid hormones show marked signs of decreased growth, slowed metabolic rates, and more susceptibility to disease.

Hypothyroidism may occur for many reasons. Iodine deficiency is less and less common but is nevertheless a cause of hypothyroidism which can result in goiters, developmental delays, and numerous other health issues. Primary thyroid disease is an inflammatory disease that destroys parts of the glandular tissue thus inhibiting the release of T3 and T4 and is another important cause of hypothyroidism. 

Early symptoms of hypothyroidism include:

  • Depression and/or fatigue
  • Poor muscle tone and/or muscle cramps
  • Carpal Tunnel Syndrome
  • Pale complexion and/or dry, itchy skin
  • Weight gain
  • Water retention
  • Increased sensitivity to cool climates

Late symptoms of hypothyroidism include:

  • Irregular or abnormal menstrual cycles
  • Lower body temperature
  • Poor memory
  • Difficulty swallowing
  • Hair loss


Hyperthyroidism and the resulting overproduction of T3 and T4 will result in the excessive stimulation of many physiological processes. Hyperthyroidism is often the result of Graves’ Disease, but may also result from toxic goiters or tumors.

Symptoms associated with hyperthyroidism include:

  • Weight loss and increased appetite
  • Tremors and/or hyperactivity
  • Excessive thirst, urination, and/or sweating
  • Depression, anxiety, fatigue, and/or apathy
  • Shortness of breath
  • Intolerance to heat