An underactive thyroid hides for years by design

The thyroid is a small butterfly-shaped gland at the front of the neck whose
hormones set the rate at which the body uses energy — breathing, heart rate,
weight, digestion, mood. Hypothyroidism is that gland not making enough, and
the consequence is that many of the body's functions slow down.

**Because it develops slowly, many people do not notice it for months or even
years.** That is the single most important fact about it: nothing announces
itself, and each symptom on its own has an ordinary explanation.

What it feels like

Fatigue. Weight gain. A puffy face. Trouble tolerating cold. Joint and muscle
pain. Constipation. Dry skin. Dry, thinning hair. Decreased sweating. Heavy or
irregular periods, and fertility problems. Depression. A slowed heart rate. A
goitre — an enlarged thyroid that makes the neck look swollen and can
interfere with breathing or swallowing.

Read as a list it is obvious. Arriving one at a time over two years, it is
not.

Where it comes from

• Hashimoto's disease — an autoimmune disorder in which the immune system
  attacks the thyroid. The most common cause.
• Thyroiditis — inflammation of the gland.
• Congenital hypothyroidism — present at birth.
• Surgical removal of part or all of the thyroid.
• Radiation treatment to the thyroid.
• Certain medicines.
• Rarely, pituitary disease, or too much or too little dietary iodine.

Risk is higher in women, over 60, after a previous thyroid problem such as a
goitre, after thyroid surgery or radiation to the thyroid, neck or chest, with
a family history of thyroid disease, within six months of a pregnancy, and
alongside Turner syndrome, pernicious anaemia, Sjögren's syndrome, type 1
diabetes, rheumatoid arthritis or lupus.

What it causes if left alone

High cholesterol. In rare cases, myxoedema coma — the body's functions
slowing to the point of being life-threatening. In pregnancy: premature birth,
high blood pressure and miscarriage, and slowed growth and development in the
baby.

Diagnosis is a medical history and physical exam, thyroid blood tests (TSH,
T3, T4, thyroid antibodies), and imaging where needed — a thyroid scan,
ultrasound or radioactive iodine uptake test.

Treatment, and the schedule that goes with it

The treatment is medicine replacing the hormone the thyroid can no longer
make. Finding the right dose follows a fixed rhythm:

Taken as instructed, the medicine usually controls the condition. **Never stop
it without talking to your provider first.**

Two notes on iodine. With Hashimoto's or another autoimmune thyroid disorder
you may be sensitive to harmful effects from iodine, so ask which foods,
supplements and medicines to avoid. And in pregnancy the requirement goes
up, because the baby takes iodine from the mother's diet — another
conversation to have rather than a rule to guess at.

*Source: National Institute of Diabetes and Digestive and Kidney Diseases,
via MedlinePlus.*