Thyroid Testing in the Philippines: TSH, T3, T4, and What Your Results Mean

Quick answer

A complete thyroid test includes TSH, Free T4, Free T3, and, when needed, thyroid antibodies called TPO and TgAb. TSH alone catches severe hypothyroidism and hyperthyroidism. It misses milder patterns, conversion problems, and early autoimmune disease.

How your thyroid works

Your thyroid is a small gland in your neck. It makes hormones that control your energy, weight, and body temperature.

Here is the chain of command. Your brain sends a signal called TRH. This tells the pituitary gland, also in your brain, to release TSH. TSH then tells your thyroid to make thyroid hormone.

Your thyroid makes mostly T4, a kind of storage form of the hormone. Your body then converts some of that T4 into T3, the active form that your cells actually use.

A full picture needs three pieces:

• The brain's signal, TSH.
• The storage form, Free T4.
• The active form, Free T3.

A TSH-only test only checks the first piece of this chain.

TSH, and why "normal" may be too wide

The standard range printed on most Philippine lab reports is 0.4 to 4.5 mIU/L. This wide range comes from testing a large group of people, some of whom already have mild thyroid problems. Many doctors now believe the healthier target is tighter, closer to 0.5 to 2.5.

That means a TSH of 4.0 can be called "normal" on your lab report. But it sits in a zone where many people still have real symptoms.

Free T4

Free T4 is the amount of storage hormone that is free to move through your blood and reach your cells.

Standard range: 0.8 to 1.8 ng/dL. Healthy target: the middle of that range.

A low Free T4 paired with a high TSH is the classic sign of an underactive thyroid.

Free T3

Free T3 is the active hormone your cells actually use.

Standard range: 2.3 to 4.2 pg/mL. Healthy target: the upper third of that range.

Many doctors see Free T3 as the number that lines up best with how you actually feel.

Here is a pattern seen often in Filipino adults. TSH looks normal. Free T4 looks normal. But Free T3 is low. This is called a conversion problem. Your body makes enough T4, but it is not turning enough of it into T3. Causes include low nutrient levels such as selenium, zinc, iron, or vitamin D, ongoing stress, eating too little for too long, being sick for a long time, or gut inflammation.

Thyroid antibodies

Antibodies are proteins your immune system makes when it attacks your own thyroid by mistake.

Anti thyroid peroxidase, or TPO. Often present in Hashimoto's disease, the most common cause of an underactive thyroid. TPO can show up years before your TSH changes at all.

Anti thyroglobulin, or TgAb. Also seen in Hashimoto's disease, often alongside TPO.

TSH receptor antibodies, or TRAb. Present in Graves' disease, the most common cause of an overactive thyroid.

Knowing your antibody status helps your doctor decide how closely to watch you, and when to step in early.

Reverse T3

Reverse T3 is a specialty test. Doctors order it for people who still have symptoms even though their standard thyroid tests look normal.

Think of reverse T3 as a brake pedal. It blocks your active T3 hormone from working properly. It tends to rise during chronic stress, illness, very low calorie eating, or while recovering from a hard time in life.

Comparing your Free T3 to your reverse T3 shows how much active thyroid hormone your body is actually able to use.

Common patterns you might see

Pattern one: healthy. TSH 0.5 to 2.5, Free T4 mid range, Free T3 upper third. Nothing to do here except test again next year.

Pattern two: mild underactive thyroid. TSH 4.5 to 10, Free T4 normal, Free T3 low or low normal. Symptoms vary and may include tiredness, weight gain, or feeling cold easily. This is often early Hashimoto's disease, so check TPO antibodies. Talk with your doctor about whether to treat now or watch closely.

Pattern three: underactive thyroid. TSH over 10, Free T4 low, Free T3 low. Symptoms are usually clear. Treatment, often a medicine called levothyroxine, is typically needed.

Pattern four: conversion problem. TSH normal, Free T4 normal, Free T3 low. Reverse T3 is often high too. You may have symptoms despite a "normal" TSH. This is common with chronic stress, strict dieting, or ongoing illness. Fixing the underlying cause, through nutrition, stress relief, or rest, often helps. Some people also benefit from T3 treatment.

Pattern five: Hashimoto's disease. TSH can swing around. TPO or TgAb antibodies test positive. The condition may be mild or severe. Treatment depends on how far it has progressed, alongside lifestyle changes like more vitamin D and better sleep.

Pattern six: Graves' disease, or an overactive thyroid. TSH is suppressed. Free T4 and Free T3 are high. TRAb often tests positive. Symptoms include weight loss, a racing heart, anxiety, feeling too hot, and shaky hands. This needs a doctor's care right away, often with medicine, radioactive iodine, or surgery.

Why thyroid testing in the Philippines often falls short

Three reasons show up again and again.

TSH-only is the standard. Most annual checkups test TSH alone. A full panel is usually an extra cost you have to ask for.

Wide standard ranges hide mild problems. Someone with a TSH of 3.5 to 4.5 is often told everything is fine, even with real symptoms.

Antibody testing is rarely included. TPO and TgAb catch autoimmune thyroid disease early. They are seldom ordered unless a doctor already suspects a problem.

The result is that many Filipino adults, especially women, are told their thyroid is fine while their tiredness, weight resistance, hair changes, and cycle changes go unexplained. If your symptoms and your TSH-only result do not match, our guide on hypothyroidism versus hyperthyroidism walks through both directions your thyroid can go.

When to get tested

• Every adult should get a baseline test once a year, especially women in their 30s and beyond.
• Test sooner if you have ongoing tiredness, weight resistance, mood changes, hair thinning, feeling cold, brain fog, or constipation.
• Test if autoimmune thyroid disease runs in your close family.
• Test before trying to get pregnant, since thyroid health affects fertility and pregnancy.
• Test after giving birth. Thyroid problems after pregnancy are common and often missed.

Food and lifestyle factors

Your thyroid needs several nutrients that can run low in Filipino diets.

• Iodine. Needed to build thyroid hormone. Iodized salt usually covers this.
• Selenium. Helps your body turn T4 into T3, and helps calm antibody levels.
• Zinc. Supports conversion and the brain's signal to your thyroid.
• Iron. Low iron, shown by ferritin under 50 ng/mL, can slow your thyroid down.
• Vitamin D. Helps calm an overactive immune system.

Ongoing stress, eating too little for too long, and long illness all make conversion worse and raise reverse T3.

What a &you Labs panel checks

A &you Labs panel covers ten categories of health markers, and thyroid health is one of them. Your report shows both the standard lab range and the healthy target range side by side, plus a doctor's plain language plan built around your results.

See the full list of biomarkers we test to check exactly what is included.

Frequently asked questions

Why does my regular checkup only test TSH?

Cost. TSH is the cheapest thyroid test, so it is often the only one included in standard checkup packages. Many doctors agree a full panel is more useful, but the cheaper test remains the default.

Are thyroid problems really more common in women?

Yes. Women get autoimmune thyroid disease far more often than men. It tends to show up in the 30s and beyond, after giving birth, and during the years around menopause.

What time of day should I test my thyroid?

TSH shifts slightly through the day and is usually highest in the morning. Test at the same time of day each time, and a morning draw is the easiest way to stay consistent.

Should I take my thyroid medicine before the test?

This depends on your doctor. Some want you to skip your morning dose until after the blood draw. Others want you to take your normal dose. Follow what your prescribing doctor tells you.

Can I have a thyroid problem even with a normal TSH?

Yes. This happens with conversion problems, where TSH and Free T4 look normal but Free T3 is low. It also happens with early autoimmune disease, where antibodies test positive before TSH ever changes. This is exactly why a full panel, not just TSH, matters.

Key takeaways

• TSH alone is not the full picture. A complete test adds Free T3, Free T4, and antibodies when needed.
• The standard TSH range, up to 4.5, is wider than the healthy target range of 0.5 to 2.5.
• Conversion problems, low Free T3 despite a normal TSH, are common with stress, dieting, and long illness.
• Thyroid antibodies can show up years before TSH ever changes.
• All adult women benefit from a yearly thyroid check.