Thyroid Health Panel

The thyroid health panel includes three tests from a single blood draw: TSH, total thyroxine (T4) and total triiodothyronine (T3). It provides a basic assessment of whether the thyroid is working normally, too little or too much. Your doctor interprets the results together with your symptoms and the medicines you take.

Who the panel is for

• people who are persistently tired, sensitive to cold, gaining weight, or have dry skin or constipation, which may indicate an underactive thyroid;
• people with restlessness, palpitations, weight loss, sweating or trembling hands, which may indicate an overactive thyroid;
• people with an enlarged thyroid or a lump in the neck;
• women with irregular periods or difficulty becoming pregnant;
• people with high cholesterol or atrial fibrillation;
• people being treated for thyroid disease, for monitoring as agreed with their doctor.

Routine thyroid checks are unnecessary for people without symptoms or risk factors. Those at greater risk are described in the article on early detection of thyroid dysfunction.

What the panel contains and shows

• TSH (thyrotropin) is secreted by the pituitary gland to stimulate thyroid function. It is the most sensitive indicator of thyroid function: when there is too little thyroid hormone, TSH rises, and when there is too much, it falls. It often changes before hormone levels move outside the reference range.
• T4 (thyroxine) is the main hormone produced by the thyroid and indicates how much hormone the gland produces.
• T3 (triiodothyronine) is the more active form of the hormone, mostly formed by conversion from T4 in other tissues. It is most useful when an overactive thyroid is suspected.

T3 and T4 in this panel are total hormones. Almost all thyroid hormone in the blood is bound to carrier proteins, while only a small proportion is free and acts in cells. Total hormones include both fractions, so their values are also affected by the amount of carrier proteins.

Total or free hormones: which panel to choose

There are more carrier proteins during pregnancy and with oestrogen-containing medicines, such as contraceptive pills or hormone replacement therapy. Total T4 and T3 may then be elevated even though thyroid function is normal. Free hormones (fT4 and fT3) are less dependent on these changes, so they are now more commonly measured alongside TSH.

There are three thyroid panels:

• Thyroid Health Panel (TSH, T3, T4): suitable when your doctor requests total hormones or when you want to compare results with previous tests performed in the same way.
• Thyroid Panel with Free Hormone Fractions (TSH, fT3, fT4): in most cases a more practical choice for assessing thyroid function and monitoring treatment, particularly if you take oestrogen-containing medicines.
• Complete thyroid panel (TSH, T3, T4, fT3, fT4, anti-TPO, anti-TG): useful during the initial assessment when the doctor wants to check both thyroid function and whether the cause is autoimmune thyroid inflammation (Hashimoto’s thyroiditis).

The usual order of thyroid tests and when antibodies are needed are explained in the article on laboratory thyroid investigations.

Preparation and sample

Blood is taken from a vein. You do not need to fast for thyroid tests, but if blood glucose or blood fats are being tested at the same time, attend fasting. It is best to attend in the morning and have follow-up tests at a similar time of day, because TSH varies slightly during the day.

• If you take levothyroxine, take your tablet after the blood draw on the day of testing. Do not stop treatment yourself.
• If you take biotin (for example, hair and nail supplements), mention this when your blood is drawn, as it may affect the results of some thyroid tests.
• Mention if you are pregnant or take contraceptive pills or hormone replacement therapy.

How results are interpreted

Reference ranges depend on the method and, for TSH, partly on age, and are printed on the report. Different limits apply during pregnancy. The most common patterns are:

• elevated TSH and low T4: an underactive thyroid (hypothyroidism), most commonly due to Hashimoto’s thyroiditis;
• elevated TSH with normal T4: subclinical hypothyroidism; the test is usually repeated after several weeks to three months because the abnormality may be temporary;
• low TSH and elevated T4 or T3: an overactive thyroid (hyperthyroidism), for example due to Graves’ disease, nodules that produce hormones independently, or thyroid inflammation;
• elevated total T4 or T3 with normal TSH: often a consequence of increased carrier proteins, for example during pregnancy or while taking the pill, rather than thyroid disease; the doctor may then request free hormones.

In people taking levothyroxine, elevated TSH most often means the dose is too low, and low TSH means it is too high. The panel does not show the cause of the disorder: this requires antibodies anti-TPO and anti-TG, ultrasound and other tests selected by the doctor.

How to arrange testing

You can come for blood collection without an appointment or referral at one of our branches throughout Croatia (listed on the Contactpage). Prices for all tests and panels are listed in the service price list.

Frequently asked questions

Are thyroid hormones shown in a blood count?

No. A complete blood count shows blood cells, not hormones. TSH and thyroid hormones must be requested separately, individually or as a panel.

Can I drink coffee before thyroid blood tests?

Yes, if no tests requiring fasting, such as glucose or blood lipids, are sampled at the same time. Otherwise, have coffee after blood collection.

What is the difference between T4 and fT4?

T4 is total thyroxine, both bound and free, while fT4 is only the free fraction, which acts in cells. Total T4 also depends on carrier proteins, so fT4 is more reliable when their amount changes, for example with contraceptive pills.

Is TSH alone sufficient for monitoring treatment?

With a stable levothyroxine dose, TSH is usually sufficient for monitoring, with fT4 if necessary. Your doctor will determine which tests to repeat and how often.