Causes

Most of patients get hypothyroidism after taken RAI 131 (Radioactive Iodine) and Thyroidectomy. We have summarized the causes as following:

Primary hypothyroidism, caused by hurt in Thyroid gland

The most common forms RAI 131 (Radioactive Iodine), Thyroid Surgery and Hashimoto's thyroiditis (an autoimmune disease).

Secondary hypothyroidism, caused by problem in Pituitary gland

Occurs if the pituitary gland does not create enough thyroid-stimulating hormone (TSH) to induce the thyroid gland to produce enough thyroxine and triiodothyronine. Although not every case of secondary hypothyroidism has a clear-cut cause, it is usually caused by damage to the pituitary gland, as by a tumor, radiation, or surgery.

Tertiary hypothyroidism, caused by problem in Hypothalamus

 Results when the hypothalamus fails to produce sufficient thyrotropin-releasing hormone (TRH). TRH prompts the pituitary gland to produce thyroid-stimulating hormone (TSH). Hence may also be termed hypothalamic-pituitary-axis hypothyroidism.

Diagnosis

To diagnose hypothyroidism, many doctors simply measure the amount of thyroid-stimulating hormone (TSH) being produced by the pituitary gland. High levels of TSH indicate that the thyroid is not producing sufficient levels of thyroid hormone (mainly as thyroxine (T4) and smaller amounts of triiodothyronine (T3)).

TSH: 0.45 - 4.50 uIU/mL

FT3 2.5 – 6.0 pmol/L

FT4: 9 – 19 pmol/L

TT3: 1.2 – 3.2 nmol/L

TT4: 65 – 155 nmol/L

T4 Free/Direct (nanograms): 0.82 - 1.77 ng/dl;

T3 (nanograms): 71 - 180 ng/dl.

* The result will be varied from lab to lab. So patients need to show the normal range of each figures.

Additionally, the following measurements may be needed:

Antithyroid antibodies (TPOAb and TGAb) — for evidence of autoimmune diseases that may be damaging the thyroid gland

Serum cholesterol — which may be elevated in hypothyroidism

Prolactin — as a widely available test of pituitary function

Testing for anemia, including ferritin

Basal body temperature

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