Parent Concerns & Support

What causes hypothyroidism?

The most common cause is due to an 'autoimmune disease' called autoimmune thyroiditis. The immune system normally makes antibodies to attack bacteria, viruses, and other 'germs'. If you have an autoimmune disease, the immune system makes antibodies against certain tissues of your body.

  • With autoimmune thyroiditis, you make antibodies that attach to your own thyroid gland which affect the glands function. The thyroid gland is then not able to make enough thyroxine, and hypothyroidism gradually develops. It is thought that something triggers the immune system to make antibodies against the thyroid. The 'trigger' is not known.
  • People with autoimmune thyroiditis have a small increased risk of developing other autoimmune conditions such as vitiligo (a skin disease that causes loss of pigment, resulting in irregular pale patches of skin) or pernicious anaemia (anemia due to vitamin B12 deficiency).

How is hypothyroidism treated?

The treatment is to take levothyroxine (thyroxine) tablets each day. This replaces the thyroxine which the thyroid gland is not making. Most people feel much better soon after starting treatment. Ideally, take the tablet on an empty stomach (before breakfast). This is because some foods rich in calcium or iron may interfere with the absorption of thyroxine from the gut. (For the same reason, don't take thyroxine tablets at the same time of day as calcium or iron tablets). Treatment is usually for life.

What are the possible complications of hypothyroidism?

If undiagnosed and untreated in childhood the child’s normal growth and brain development may be affected. There may also be an increased risk of developing heart disease. This is because a low thyroxine level causes the blood lipids (cholesterol, etc) to rise. Hypothyroid coma (myxoedema coma) is a very rare complication. However, with treatment, the outlook is excellent, symptoms usually go, and you are very unlikely to develop any complications.

How is hypothyroidism diagnosed?

There are several tests of thyroid function known as ‘thyroid function tests’ (TFTs). 
These include blood sample measurement of:

  • Thyroid-stimulating hormone (TSH). This hormone is made in the pituitary gland. It is released into the bloodstream. It stimulates the thyroid gland to make thyroxine. If the level of thyroxine in the blood is low, then the pituitary releases more TSH to try and stimulate the thyroid gland to make more thyroxine. Therefore, a raised level of TSH means the thyroid gland is underactive and is not making enough thyroxine.
  • Thyroxine (T4). A low level of T4 confirms hypothyroidism.
  • Thyroid antibodies (TPO) thyroid antibodies harm a person’s own thyroid gland and prevent it producing enough thyroxine

Note: some people have a raised TSH but have a normal T4. This means that enough thyroxine being produced but the thyroid gland needs extra 'stimulation' from TSH to maintain appropriate levels of thyroxine in the body.

What causes Hyperthyroidism?

Hyperthyroidism is the term for overactive tissue within the thyroid gland, resulting in overproduction and thus an excess of circulating free thyroid hormones: thyroxine (T4), triiodothyronine (T3), or both. This thyroid disorder is caused by an antibody-mediated auto-immune reaction, but the trigger for this reaction is still unknown.

How is Hyperthyroidism treated?

The treatment of hyperthyroidism is by medication (carbimazole). This medication usually stops the overproduction of thyroid hormones. In very few cases it may be necessary to remove part of the gland to treat the problem.

Thyroid Disorder among people with Down syndrome - Notes for Parents & Carers 2008 (Down Syndrome Association – Medical Series)

References
Thyroid Dysfunction in Down’s Syndrome and Screening for Hypothyroidism in Children and Adolescents Using Capillary TSH Measurement. J. Murphy, M. Philip, S. Macken, J. Meehan1, E. Roche, P.D. Mayne, M. O’Regan, H.M.C.V. Hoey. Journal of pediatric endocrinology & metabolism ISSN 0334-018X 2008, vol.21,n2,pp.155-163.

Guidelines for the Medical Management of Irish Children and Adolescents with Down Syndrome, Irish Medical Journal, Feb 2005, Vol 98 No 2; 48-52. Murphy J, Hoey HMCV, Philip M, Roche EF, Macken S, Mayne P, Duff D, O’Keefe M, McShane D, Fogarty E, O’Regan M.