Effect of Thyroid hormone excess on other systems:


Nervous System:

Nervousness, emotional lability, increased activities, fatigue, loss of sleep may occur in hyperthyroidism. Mental disturbance is sometimes severe & may be in the form of manic depressive, schizoid or paranoid reactions. Due to the increased activities, during the interview patients frequently change his or her positions. Movements are quick, jerky, exaggerated and most of the times purposeless. These findings are characteristic of thyrotoxic patients. Fine tremor of hands, tongue or closed eyelids may appear and seizure frequency is increased. Children may have decreased school performance.


Muscles and Skeletal (Bones) System:

Generalized wasting of muscles is seen in thyrotoxic patients. The weakness is most prominent in the proximal muscles of the limbs, causing difficulty in climbing stairs or fatigue from minimal exertion such as using a hairdryer or lifting an infant. Muscle involvement occurs more commonly in men than women. Other muscles like muscles of trunk, face, eyes may be involved in severe forms. The strength of the muscles return to normal after treatment but muscle mass takes longer to recover. Calcium from bones may be lost leading to demineralization of bones and may cause fractures seen in elderly woman with thyrotoxicosis.


Gastrointestnal System:

An increase in appetite is common & the frequency of bowel movements is increased. Slight malabsorption of fat occur in thyrotoxic patient.


Reproductive System:

In early life, thyrotoxicosis causes delayed sexual maturation. After puberty, thyroid influences the reproductive function mainly in females. Menstrual flow is decreased or stopped in thyrotoxicosis. Fertility may be reduced & risk of miscarriage is there.

Female like breasts in males (Gynecomastia) and erectile dysfunction is seen in upto 10% of thyrotoxic men.


Cardiovascular System:

Thyroid hormone excess always presents with increase in heart rate. Patient often experiences palpitations. The heart sounds are enhanced. 2 to 20% of thyrotoxic patients are having irregular heart rate in the form of atrial fibrillation. Patients may have heart failure, or swelling of the limbs without heart failure.



Eye signs and changes are among one of the most distinguishing features of thyroid hormone excess in any form. There occurs the retraction of upper and lower eye lids and a rim of sclera (white layer) is visible between the lid and the limbus. It is responsible for the typical staring look of the patient. Movements of the lids lag behind the globe. Protrusion of eye balls may also occur in infiltrative autoimmune thyroid disease.

Picture 3 Jayshree Swain

Staring look in Hyperthyroidism


Skin and Hairs:

Warm and moist feel of the skin with excessive sweating are one of the most characteristic changes in patients with long standing thyrotoxicosis. Complexion of skin also changes. The hairs are fine and friable and there is more hair loss. Nails are soft & brittle.



Effect of Thyroid hormone deficiency on other systems:

Hypothyroidism can affect all organ systems but the severity depends on the degree of hormone deficiency.


Skin and hairs:

Skin becomes puffy in appearance, pale & cool. In severe cases characteristically boggy with non pitting oedema that is more evident around the eyes, upper aspect of the hands and feet and above the collar bone (clavicle). Wounds tend to heal slowly with tendency to easy bruising. Hairs become dry & brittle with lack of luster and tend to fall. Growth of hairs is also retarded. Hair may be lost on outer side of the eyebrows.

Picture1 Jayshree Swain 

Facial swelling in Hypothyroidism


Cardiovascular System:

Heart rate and cardiac output is decreased and, blood volume is reduced. Decrease in blood flow to the tissues leads to the coolness of the skin. In severe cases heart size is enlarged, heart sounds are diminished due to accumulation of fluid around the heart. It is frequently associated with cholesterol abnormality which improves after treatment with thyroid hormones.


Respiratory System:

Obstructive sleep apnea is common but reversible with treatment. Maximum breathing capacity of lungs is reduced. In severe cases, respiratory muscles become weak, patient may have less oxygen in blood and there can be deposition of fluid in the chest cavity.


Gastrointestinal System:

Appetite is usually reduced and gut movements are decreased leading to constipation. Complications like faecal impaction, gaseous distention, colicky pain and vomiting may occur. Fluid may be deposited in abdomen and is usually associated with deposition of fluid around other organs also like heart and lungs etc. Gastric acid secretion is also decreased.


Nervous System:

Thyroxine is an essential hormone for the development of nervous system. Thyroid hormone deficiency at birth or before (when child is inside mother’s womb) can lead to impaired brain development. If it is not corrected early, the damage is irreversible.

In thyroid hormone deficiency, all intellectual functions are slowed. Loss of initiative, lethargy, increased sleep, memory defects, slowness of speech, forgetfulness etc. are the common presentations in adults.


Reproductive System:

Sexual development is influenced in both the sexes. If the child is hypothyroid from the early life there is a delay in the onset of puberty followed by irregular menstrual cycles (in girls). Rarely, early puberty or expression of milk from mammary glands may occur. Decrease in sexual desire, failure of ovulation, decreased fertility, increased spontaneous abortion, miscarriages and preterm delivery are the sequelae seen in adult women. Hypothyroidism in men may cause decrease in sexual desire too along with erectile dysfunction and decrease in sperm counts in semen. Hypothyroidism may also cause infertility in both sexes and is an important cause of marital disharmony.


Muscular System:

Slowness of movement is seen in hypothyroid patients due to delayed muscle contraction and relaxation. Stiffness and aching of muscles are common. Muscluar symptoms are worsened by cold temperatures.

Picture2 Jayshree Swain

Muscle swelling in Hypothyroidism


Skeletal system:

For normal growth and maturation of the skeleton, thyroid hormone is very much essential. Deficiency of thyroid hormone in early life leads to dwarfism in which the limbs are disproportionately short in relation to the trunk. Children with prolonged period of thyroid hormone deficiency, even after adequate treatment, do not reach the predicted height.


This page is edited by Dr. Jayshree Swain who is an Expert Endocrinologist. Dr. Swain is working as a Consultant Endocrinologist at AMRI Hospital, Bhubaneswar, Odisha (India).