Original of this article was published on ZRT Laboratory Blog. Last reviewed: May 2026.
The average person who can’t lose weight — despite eating right and exercising — is generally frustrated and frankly stumped. For many, diet and exercise have always proven effective, and yet now, for some reason, they don’t. Sometimes just a little. Sometimes not at all.
Those who dig deeper often find that weight problems could be due to a sluggish thyroid. Feeling an inkling of hope, many ask their doctors to run a test, and lo and behold the results often come back normal. How can that be?
These results tend to stun — especially when weight gain continues to be an issue and/or we suffer from other hypothyroid hallmarks: feeling cold, old and depressed. Given that so many symptoms of low thyroid overlap with other hormone imbalances, we may not get the answers needed unless we find a healthcare provider who goes beyond the standard TSH test to address thyroid imbalances in the greater context of hormone imbalance.
Why a Standard TSH Test Is Not Enough
Our bodies produce more than one thyroid hormone. The most abundant is thyroxine (T4), a prohormone, which converts to triiodothyronine (T3), the most active thyroid hormone in the body. We need our body to make adequate levels of these two hormones since we rely heavily on them for an active metabolism.
Testing TSH alone is not going to give us the whole story because it does not take active thyroid levels into account. Nor can a single thyroid test identify imbalances of the steroid or adrenal hormones that serve to seriously inhibit thyroid function. Discovering how well our thyroid is actually working requires a big picture assessment of all hormone levels that matter.
Our Thyroid Test Kit | Specialist Doctor Report Included measures TSH, Free T3 and Free T4 from a simple at-home blood spot sample — with a specialist doctor report to help you understand whether your thyroid is converting T4 to active T3 effectively, and what may be getting in the way.
The Hidden Enemies of Thyroid Function
When it comes to a healthy thyroid, the efficient conversion of the inactive precursor T4 to active T3 has to occur — so anything that interferes with that crucial conversion process will decrease thyroid function, slow metabolism and trigger a raft of low thyroid symptoms. From hormone imbalances to mineral deficiencies and environmental pollutants, a range of factors can interfere with thyroid function:
- Oestrogen dominance — Thyroid problems are more prevalent in women, particularly those in the menopause transition. Excess oestrogens bind up active thyroid hormones.
- Elevated cortisol stress hormones — High cortisol directly impairs T4 to T3 conversion.
- Iodine deficiency — Iodine is a key structural component of both T3 and T4.
- Selenium and zinc deficiency — Both are required for thyroid hormone synthesis and activation.
- Vitamin D deficiency — Low vitamin D is consistently associated with thyroid disorders.
- Arsenic or mercury toxicity — Heavy metals deplete iodine and selenium, compounding thyroid suppression.
- Xenoestrogen burden — Environmental chemicals that disrupt oestrogen metabolism and block thyroid receptors.
For those concerned about the interaction between cortisol and thyroid function, our Thyroid & Cortisol Test Kit measures both thyroid markers and cortisol from a single at-home sample — making it easy to identify whether stress hormone elevation is a key driver of thyroid suppression.
For a comprehensive view that also covers iodine, selenium, arsenic and mercury alongside thyroid markers, our Thyroid, Heavy Metals & Essential Elements Test provides the most complete picture of the nutritional and toxic element factors affecting thyroid health — all from a simple at-home sample.
Taking action to target and take out those hidden saboteurs of thyroid health can help us master the thyroid game.
Original of this article was published on ZRT Laboratory Blog.