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3.5 minute

03-10-2024 Team Medicover endocrinology

The thyroid is a small gland in your neck, but it has a big impact on how your body works. It produces hormones that help control your metabolism, energy levels, and even your heart rate. Three key hormones are involved when we talk about thyroid health: T3 (triiodothyronine), T4 (thyroxine), and TSH (thyroid-stimulating hormone).

Whether you're dealing with fatigue, unexplained weight changes, or mood swings, checking your thyroid levels might be the first step toward answers. In this article, we’ll break down what these hormones do, what their normal ranges are — including for women, by age, and in newborns — and what your results might mean.

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Let’s start with the basics:

T3 (Triiodothyronine): This is the active thyroid hormone that affects your metabolism.

T4 (Thyroxine): This is a storage hormone that your body converts into T3 when needed.

TSH (Thyroid-Stimulating Hormone): Made by the pituitary gland, TSH tells your thyroid to produce T3 and T4.

When these hormone levels are off, you may feel it in your energy, mood, and overall health.

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Women are more likely than men to experience thyroid problems, especially during pregnancy, after childbirth, or around menopause. Here's what’s typically considered normal for adult females:

Hormone

Normal Range

TSH

0.4 – 4.0 mIU/L

Free T3

2.0 – 4.4 pg/mL

Free T4

0.8 – 2.0 ng/dL

Symptoms of thyroid imbalance in women often show up as menstrual irregularities, fatigue, hair thinning, or mood swings. If you’ve noticed any of these, a thyroid test may be helpful.

Thyroid hormone levels naturally shift as we age. Here's a quick look at what's normal across different age groups:

Age

TSH (mIU/L)

Free T4 (ng/dL)

Free T3 (pg/mL)

1–5 years

0.7 – 6.4

0.8 – 2.0

2.6 – 5.1

6–10 years

0.6 – 5.5

0.8 – 1.9

2.7 – 5.2

11–18 years

0.5 – 4.8

0.8 – 1.8

2.8 – 4.4

Age

TSH (mIU/L)

Free T4 (ng/dL)

Free T3 (pg/mL)

18–30 yrs

0.4 – 3.5

0.9 – 2.1

2.3 – 4.2

31–60 yrs

0.5 – 4.0

0.8 – 2.0

2.3 – 4.1

60+ yrs

0.6 – 4.5

0.7 – 1.8

2.0 – 3.8

As we age, TSH levels tend to rise slightly, which can be perfectly normal if you're not experiencing symptoms.

Thyroid function is just as important for newborns — if not more — because it's crucial for brain development and growth. That’s why thyroid testing is often part of routine newborn screening.

Hormone

Normal Range (Newborns)

TSH

1.0 – 39.0 mIU/L

Total T4

10 – 26 µg/dL

Free T4

1.1 – 2.3 ng/dL

Free T3

1.5 – 4.2 pg/mL

Right after birth, it’s common for TSH to spike, then come down to normal levels in the next few days. If TSH stays high, further tests may be needed.

Your thyroid can be underactive (hypothyroidism) or overactive (hyperthyroidism), and each condition comes with its own set of symptoms.

If you’re experiencing a few of these symptoms consistently, it’s worth getting your thyroid checked.

A range of conditions and lifestyle factors can disrupt thyroid hormone production.

Interpreting thyroid test results isn’t always straightforward. Here’s a general guide:

High TSH + Low T4 = Hypothyroidism

Low TSH + High T4 = Hyperthyroidism

Normal TSH + Abnormal T3/T4 = Possible issue with conversion or pituitary function

That’s why it’s important not to self-diagnose — a healthcare provider can look at the full picture, including your symptoms and history.

You might want to consider a thyroid test if you have:

Routine screening is also recommended during pregnancy and for women over 35.

Treatment depends on whether your thyroid is overactive or underactive:

Hypothyroidism is usually treated with levothyroxine, a synthetic version of T4.

Hyperthyroidism may require antithyroid drugs, radioactive iodine, or even surgery in some cases.

In both conditions, lifestyle factors like diet, stress management, and sleep can support better thyroid health.

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Understanding your T3, T4, and TSH levels is an important step in taking charge of your health. Whether you’re looking into the T3 T4 TSH normal range in females, exploring how these levels change by age, or even learning about thyroid function in newborns, the key takeaway is: know your numbers and talk to your doctor if something feels off.

With proper testing and early treatment, most thyroid conditions can be effectively managed, helping you feel more like yourself again.

Why is it important to monitor thyroid levels?

Regular monitoring can help identify thyroid dysfunction early, allowing for timely treatment.

What do high TSH levels indicate?

High TSH levels usually indicate hypothyroidism, meaning your thyroid isn’t making enough T3 and T4. The pituitary gland produces more TSH to try to stimulate the thyroid. Common symptoms include fatigue, weight gain, and feeling cold.

How often should I test my thyroid levels?

If you have normal thyroid levels, testing every 1–2 years is sufficient. If you’re on thyroid medication or have symptoms, your doctor may recommend more frequent testing, such as every 3–6 months.

Can diet or lifestyle affect thyroid hormone levels?

Yes. Iodine intake, stress, sleep, and certain medications can affect thyroid hormone levels. A balanced diet with adequate iodine and selenium supports thyroid health.

What should I do if my T3, T4, or TSH levels are abnormal?

Always consult an endocrinologist or primary care provider. Treatment may include medication, lifestyle changes, or further diagnostic tests to determine the underlying cause.