If your doctor suspects hypothyroidism, tests can be performed to check how well the thyroid gland is functioning. Levels of T4 in the blood are measured, along with thyroid-stimulating hormone (TSH) that is produced by the pituitary gland. High levels of TSH suggest that the thyroid is underactive and that the pituitary is overcompensating by making excess hormones to stimulate the thyroid gland.
With secondary hypothyroidism, the pituitary gland isn't functioning properly and T4 levels in the blood are low. In this case, TSH levels can be low or inappropriately normal, meaning that levels are normal when a doctor wouldn’t expect them to be normal based on a person’s medical condition.
Thyroid scans, using radioactive iodine or technetium, allow doctors to see the thyroid gland and identify areas that are less active. Thyroid ultrasound scans provide a detailed anatomic imaging of the gland, and can identify lesions (e.g. nodules, cysts), provide accurate size measurement, and show blood flow properties throughout the gland.
Treating hypothyroidism requires replacing hormones with synthetic or natural thyroid hormones. The easiest and most effective thyroid hormone replacement involves a synthetic form of T4 that is taken orally (by mouth). The tablets are available in a variety of strengths, and doses are adjusted for each individual until the correct hormone levels in the blood are reached and there is a satisfactory control of symptoms.
So-called "natural" thyroid supplements, which usually contain ground-up thyroid glands from animals, are rarely used now. This is because they can cause allergic reactions and do not provide a consistent dose of T4.
Large doses of T4 can have serious side effects. Age- and body weight-appropriate doses are therefore given at first and slowly increased until levels of T4 and TSH in the blood are back to normal.
People with mild hypothyroidism might feel fine and not require treatment, while others will be bothered by symptoms and require treatment. Hypothyroidism tends to get worse over time and even mild cases should be regularly monitored. Individuals taking small amounts of thyroid hormones may need to have their doses increased with time. Beyond a certain age, seniors sometimes need lower doses of T4.
If a dysfunctional pituitary gland is the cause of hypothyroidism, it will need to be treated. The pituitary controls many other glands in the body as well, and several medications may be needed if a person has other pituitary hormonal disorders.
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