Thyroid Disorders and Down syndrome (31 for 21, Day 8)

Many people with Down syndrome have issues with their thyroid;  it is one of the most prevalent conditions associated with Trisomy 21.  Occurring spontaneously in the general population, once it would have meant a very short life span and if untreated in childhood, "cretinism".  However, now a malfunctioning thyroid is easily detected and easily treated. 

The Thyroid Gland

The thyroid gland is a large butterfly shaped gland located in the neck along the trachea.  One of the largest of the endocrine glands, it regulates metabolism through the secretion of hormones.  The thyroid controls how and when the body makes proteins, uses energy and determines how sensitive the individual is to other hormones. The most prevalent are triiodothyronine (T₃) and tetraiodothyronine or thyroxine (T₄);  the body creates these from iodine and tyrosine.

TSH (or Thyroid Stimulating Hormone) is released by the pituitary gland in the brain.   This tells the thyroid to release more T₃ and T₄.  Thyrotropin Releasing Hormone (TRH) is released by the hypothalamus and stimulates the pituitary to release TSH.  In order:

Hypothalamus releases TRH ----> Pituitary releases TSH ----> Thyroid releases T₃ and T₄

Usually, if problems occur with the thyroid, it is because it is under active (hypothyroidism) or because it is overactive (hyperthyroidism).

Hypothyroidism

Hypothyroidism exists when the thyroid gland does not produce enough thyroid hormones.  This could be due to a break in the hormone-releasing chain (above), a missing or damaged thyroid gland or even stress.  It can be classed as sub-acute, where the TSH levels are slightly lower yet the body has normal levels of T₃ and T₄.  A lowered serum TSH (determined by a blood test) is a definitive sign of an under active thyroid.

Symptoms of mild hypothyroidism include:

Cardiac:  low heart rate
Dermatological:  dry and itchy skin, brittle fingernails
Endocrine:  galactorrhea, high serum prolactin 
Gastrointestinal:  constipation
Mental/Neurological:  rapid thoughts, depression
Metabolism:  weight gain, water retention, fatigue, low temperature, high cholesterol, sensitivity to cold.
Musculoskeletal:  muscle cramps, joint pain, hypotonia
Reproduction and Sexuality: dysmenorrhea, female infertility

As thyroid levels continue to drop, more severe or later symptoms may occur.  These include:

Cardiac: diminished heart rate (with less cardiac output)
Dermatological:  Dry puffy skin (especially on face), thinning eyebrows, hair loss, yellowing of the skin
Endocrine:  goiter, hypoglycemia, gynocomastia,
Gastrointestinal: swallowing problems, thickened tongue 
Mental: memory problems, attention span problems, irritability, mood instability, psychosis
Metabolism:  anemia, excessive sleeping 
Pulmonary:  shortness of breath, hoarseness
Sensory:   decreased smell and taste, deafness
Reproduction and Sexuality:  decreased libido

Urinary:  decreased kidney function

An under active thyroid can be treated by supplementing with oral thyroxine replacement therapy.

Myxedema Coma:

This type of coma occurs with long term, untreated hypothyroidism and can be fatal.  Alhough it can be brought on by very low thyroxine levels, it is generally precipitated (especially in the elderly) by a cardiac event, congestive heart failure, a stroke, drug toxicity,  trauma or the like.  This coma is characterized by the "hypos":  hypoglycemia, hyponatremia, hypoventilation, hypotension, hypothermia and bradycardia.  This is generally treated by giving large doses of thyroid hormones as well as managing the other body symptoms. 

Hyperthyroidism

This condition exists when there is too much thyroid hormone secreted.  This could occur for many reasons, including gland malfunction, an inflammation of the thyroid (Thryroiditis) and over-consumption of thyroid replacement medication.  As the treatment varies based on the source of the excess hormones, both bloodwork and uptake studies are usually performed.

As the thyroid controls metabolism, an excess of thyroid medication causes all body systems to speed up.  Symptoms of an overactive thyroid include:

Cardiac:  increased heart rate, palpatations
Gastrointestinal:  hypermotility, 
Mental:  anxiety, 
Metabolism: weight loss,
Neurological:  tremor

As time goes on and the levels increase further, you may find an increase of these symptoms plus:

Cardiac: arrythmias
Dermatological: hair loss, pretibial myxedema, sweating
Endocrine:  hypoglycemia, gynaecomastia
Gastrointestinal:  nausea, vomiting, diarrhea
Mental: irritablilty, apathy, delerium, 
Metabolism: weakness, fatigue, hyperactivity 
Musculoskeletal: muscle aches, joint pain, myopathy, 
Neurological: chorea, myasthenia gravis
Pulmonary: dyspnea 
Sensory:  intolerance to heat, polydipsia
Reproduction and Sexuality:  loss of libido, amenorrhea, feminization 
Urinary:  polyuria

An overactive thyroid can be treated in many ways, including thyroid inhibiting medication, radioactive iodine therapy to damage and inhibit the thyroid and partial and total thyroidectomy.

Thyroid Storm:

Also known as a thyrotoxic crisis, a thyroid storm occurs when the thyroid levels are extremely high and the patient becomes stressed.  If not treated aggressively, thyroid storm is fatal.  Symptoms include:  hyperthermia (>40 degrees C), arrhythmias, vomiting, diarrhea, dehydration, tachycardia and coma (followed by death).  This is treated by maintaining fluid balance, decreasing the overall level of thyroid hormones and stabilizing the heart using specialized drugs. 

Thyroid Disease and Down syndrome

Although thyroid disease occurs very frequently in the general population, there seems to be a high incidence (especially of hypothyroidism) in the Down syndrome community.  The chance that a person with DS develops hypothyroidism is twenty-eight times higher than a person without.  There is also a significantly higher incidence of autoimmune thyroiditis, which would be an indication to test for thyroid antibodies in those with DS along with monitoring TSH, T₃ and T₄ levels.  If discovered early, thyroid disease can be treated easily and should not pose a problem for everyday life.

Leshin, Len. "The Thyroid and Down Syndrome." Down Syndrome: Health Issues. 1996. Web. <http://www.ds-health.com/>.

Prasher, Vee. Down Syndrome and Thyroid Disorders: A Review. Down Syndrome Education International, 2012. Down Syndrome Education International. Web. <http://www.dseinternational.org/en/gb/>.

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