I feel awful but my GP says my thyroid is normal — what's going on?

A normal TSH doesn't always mean nothing is wrong — it means the thyroid axis itself looks balanced on that particular test. Fatigue, weight changes, brain fog, low mood, cold intolerance and dry skin overlap with many other conditions: iron or vitamin B12 deficiency, vitamin D deficiency, sleep apnoea, depression, perimenopause, coeliac disease, chronic stress, and poor sleep. About 10% of people on adequate levothyroxine still report ongoing symptoms despite biochemically normal results. The next step is rarely 'more thyroid medication' — it's usually a broader workup. Discuss with your GP before changing or stopping levothyroxine.

What's subclinical hypothyroidism and do I need treatment?

Subclinical hypothyroidism means TSH is mildly raised (usually 4–10) but free T4 is still in the normal range. Whether to treat depends on the TSH level, symptoms, antibody status, age, and pregnancy plans. The Endocrine Society of Australia and Therapeutic Guidelines suggest treating when TSH is ≥10, when there's pregnancy or pregnancy planning, when thyroid antibodies are positive with symptoms, or when there's a goitre. For mildly raised TSH in older adults without symptoms, two major trials (TRUST and IEMO80+) showed no quality-of-life benefit from starting levothyroxine. Often the right plan is to recheck in 1–3 months — about 30% normalise without treatment.

How should I take levothyroxine for it to work properly?

Levothyroxine absorption is sensitive to timing and what's in your stomach. The standard approach is one tablet at the same time daily on an empty stomach, then wait at least 30–60 minutes before eating, drinking coffee, taking calcium, iron, multivitamins, antacids or proton pump inhibitors. Coffee and calcium are the two biggest practical absorption blockers. A bedtime dose at least 3 hours after the evening meal is an alternative if morning timing doesn't work. Brand consistency matters — Eutroxsig, Eltroxin and Oroxine are treated by the TGA as bioequivalent but some people notice a difference when brands switch, so request the same brand at each refill where possible.

I'm planning pregnancy — do I need to change my dose?

Yes — preconception planning matters more than most people realise. The Endocrine Society of Australia and the international ATA guidelines suggest a preconception TSH below 2.5 mIU/L. Once pregnancy is confirmed, the levothyroxine dose typically needs to go up by 25–30% almost immediately, with TSH checked monthly through the first half of pregnancy. The reason is that maternal thyroxine demand jumps in early pregnancy, and adequate maternal thyroid hormone matters for fetal brain development in the first trimester. If you're on levothyroxine and trying to conceive, book a preconception review — your GP will usually re-check TSH and plan the dose-increase strategy in advance.

Do I have to take a tablet forever? Are there natural alternatives?

For Hashimoto's and most other causes of established overt hypothyroidism, yes — the gland's hormone-making capacity has been damaged and won't return. Levothyroxine isn't a drug in the typical sense; it's the same molecule (T4) the body normally makes. Combination T4/T3 therapy and desiccated thyroid (Armour, NDT) sit in a more complicated space — Cochrane reviews have not shown clear benefit over T4 alone, desiccated products are not on the Australian Register of Therapeutic Goods, and where T3 is used it's generally specialist-initiated. The body isn't broken; the gland is just under-producing one hormone, and replacing it precisely is what the medication does. Address absorption, brand consistency, and the other contributors to fatigue before assuming the medication is the problem.

What about iodine, selenium, and supplements for Hashimoto's?

Iodine: Australia has had mandatory iodine fortification of bread since 2009 and most adults don't need supplemental iodine. Pregnant and breastfeeding women are an exception — the NHMRC recommends 150 mcg/day in pregnancy and lactation. Mega-dose iodine (kelp, seaweed supplements) can actually trigger or worsen autoimmune thyroiditis and is best avoided. Selenium: there is modest evidence (small randomised trials and a Cochrane review) that 100–200 mcg/day selenium may reduce anti-TPO antibody titres in Hashimoto's, though clinical benefit is uncertain — a time-limited trial is reasonable but watch for selenosis at high doses. Vitamin D and iron deficiency are common in autoimmune disease and worth correcting if low. None of these replace levothyroxine when it's indicated.

Hypothyroidism

Hypothyroidism: TSH, levothyroxine, and the grey zone in between

By Dr HB Lo, FACRRM Reviewed 21 May 2026 13 min read

Hypothyroidism is an under-active thyroid, most often from Hashimoto's autoimmune thyroiditis in Australia. Diagnosis is biochemical: raised TSH with low or normal free T4. About 2% of AU adults have overt hypothyroidism; another 5% sit in the subclinical grey zone.

Treatment is a daily levothyroxine tablet (Eutroxsig, Eltroxin, Oroxine) on an empty stomach, adjusted by TSH every 6–8 weeks until stable. Once stable, annual TSH is enough.

The harder territory: subclinical hypothyroidism (TSH 4–10), persistent symptoms despite a normal TSH, and pregnancy planning — where thresholds tighten and the conversation gets individual.

What hypothyroidism actually is

The thyroid gland sits at the front of the neck and produces two hormones — T4 (thyroxine) and a smaller amount of T3 (triiodothyronine) — that set the body’s metabolic tempo. Production is regulated by TSH (thyroid-stimulating hormone) released from the pituitary in the brain. When the thyroid under-produces, the pituitary senses the shortfall and pushes TSH up. That is why a raised TSH is the first signal of under-active thyroid function — it’s the brain shouting at a sluggish gland.

In Australia and most iodine-replete countries, the dominant cause is Hashimoto’s thyroiditis — an autoimmune condition where the body’s own antibodies (anti-TPO and anti-Tg) gradually damage the thyroid. Other causes include previous thyroid surgery or radioiodine treatment, drug-induced (lithium, amiodarone, interferon, immune checkpoint inhibitors used in oncology), postpartum thyroiditis, congenital, and rarer pituitary or hypothalamic causes. Iodine deficiency is uncommon in Australia since mandatory iodine fortification of bread came in in 2009, per the NHMRC.

A. Core clinical — the AU primary-care framework

Who turns up

The classic clinical picture is a woman in her 40s, 50s or 60s with fatigue that doesn’t lift, gradual weight gain, cold intolerance, constipation, dry skin, hair thinning, heavier or more irregular periods, low mood, cognitive slowing, or a goitre noticed by a partner or family member. The catch is that none of these symptoms is specific — they overlap heavily with perimenopause, depression, iron-deficiency anaemia, sleep apnoea, vitamin D deficiency, and simple chronic life-stress. The diagnosis is biochemical, not clinical.

Prevalence in Australian adults is roughly 2% for overt hypothyroidism and another 5% in the subclinical band, with a female-to-male ratio around 5:1. Prevalence rises with age — about 10% of women over 60 sit somewhere on the spectrum.

History a GP will take

A focused history covers symptom pattern and duration, prior thyroid surgery or radioiodine, family history of thyroid or other autoimmune disease (type 1 diabetes, coeliac, vitiligo, Addison’s, pernicious anaemia all cluster together), medications (lithium, amiodarone, interferon, immune checkpoint inhibitors), pregnancy plans, postpartum status, and diet — including any high-dose iodine or kelp products.

Examination

The examination is brief — heart rate (often slow), thyroid palpation for goitre or nodules, skin (dry, cool, sometimes puffy around the eyes), and reflexes (a delayed-relaxation “hung-up” reflex is a classic but uncommon finding). HealthDirect and the Australian Thyroid Foundation both have useful patient-facing summaries.

The blood tests

The Australian primary-tier framework (Therapeutic Guidelines, RACGP, and the Endocrine Society of Australia) all converge on the same staged approach:

First-line: TSH is the single most sensitive test. The TSH–T4 feedback loop is log-linear, so small drops in T4 cause a much larger jump in TSH.
If TSH is abnormal: free T4 (most labs reflex-test this automatically when TSH is out of range).
Free T3 is not useful in routine hypothyroidism workup — it is reserved for hyperthyroidism or suspected pituitary causes.
Anti-TPO (and anti-Tg) antibodies to confirm autoimmune aetiology and estimate progression risk — antibody-positive subclinical hypothyroidism progresses to overt disease faster than antibody-negative.
Thyroid ultrasound is not routine — it is reserved for a palpable nodule, asymmetric goitre, or compressive symptoms.

A practical pitfall worth knowing: biotin supplements (common in hair and nail products) can interfere with the laboratory assay and produce misleading results. The Therapeutic Goods Administration and most pathology providers recommend stopping biotin for at least 48 hours before testing.

When to test in general practice

There is no Australian recommendation for universal screening of asymptomatic adults. Testing is targeted: symptoms suggestive of hypothyroidism, a goitre, a family history with new symptoms, a personal history of autoimmune disease, women planning pregnancy or in early pregnancy, postpartum women with persistent symptoms, and patients on lithium, amiodarone, or immune checkpoint inhibitors per eTG and NPS MedicineWise.

B. Subclinical hypothyroidism — when to treat

Subclinical hypothyroidism — TSH mildly raised (commonly 4–10) with free T4 still in range — is the area of greatest uncertainty in general practice, and an area where patient preferences and pregnancy plans matter as much as the number on the page.

What the evidence shows

Two large randomised trials are the load-bearing data points the Endocrine Society of Australia cites:

TRUST (NEJM 2017) randomised adults 65+ with subclinical hypothyroidism to levothyroxine versus placebo. Despite normalising TSH, there was no improvement in hypothyroid symptoms or tiredness scores at one year.
IEMO80+ (JAMA Intern Med 2019) repeated the question in adults ≥80 and reached the same conclusion: no quality-of-life benefit from starting levothyroxine.

The cardiovascular-risk question is more contested. Some observational data link subclinical hypothyroidism to higher cardiovascular events at TSH levels >10, but at TSH 4–10 the signal is weak and inconsistent — and the trials above did not show treatment improved outcomes.

Where AU guidance lands

Following Therapeutic Guidelines and the Endocrine Society of Australia, the practical default is:

Treat if TSH is ≥10, regardless of symptoms.
Treat if pregnant or planning pregnancy.
Treat if anti-TPO antibodies are positive with symptoms or a clearly rising TSH trend.
Treat if there is a significant goitre.
Otherwise watch and recheck in 1–3 months, then 6–12 months. About 30% of mildly raised TSH results normalise on repeat without any treatment.

The pregnancy-planning exception

The threshold tightens for women planning pregnancy. The Endocrine Society of Australia and the ATA 2017 pregnancy guideline both recommend a preconception TSH below 2.5 mIU/L. The TABLET trial (Lancet 2019) did not show benefit from levothyroxine in women with TSH 2.5–4 and thyroid antibodies who were trying to conceive — so universal treatment in that range isn’t justified — but the trial reinforces that the conversation should be had, antibody-positive women should be flagged, and TSH >4 with positive antibodies remains a treat decision.

C. Levothyroxine dosing and monitoring

Starting dose

The standard initial dose for a young, otherwise-well adult is around 1.6 mcg per kilogram per day, rounded to the nearest available tablet strength (50, 75, 100, 200 mcg in Australia). The Australian Medicines Handbook and Therapeutic Guidelines both reduce this in two situations:

Older adults (>65) — start at 25–50 mcg/day and titrate up slowly. The risk is precipitating angina or atrial fibrillation in someone with undiagnosed coronary disease.
Known ischaemic heart disease or severe long-standing hypothyroidism — start lower again at 12.5–25 mcg/day, titrating every 4–6 weeks.

Doses are then adjusted by 12.5–25 mcg in either direction based on TSH.

When to recheck

The body takes about six weeks to reach a steady state after any dose change because of the long half-life of thyroxine. Checking TSH earlier than that gives a misleading reading. Standard practice:

TSH 6–8 weeks after every dose change.
Annually once stable.
Sooner if pregnant, on a new interacting medication, or if weight has shifted by 10% or more.

TSH target

For the general adult population, target a TSH between 0.5 and 4.0 mIU/L. For pregnancy and preconception, a tighter range below 2.5 mIU/L applies. For adults over 70, eTG accepts a slightly higher upper bound (around 6 mIU/L) to avoid over-replacement, which carries its own risks of atrial fibrillation and accelerated bone loss.

Brand consistency

Three Australian brands of levothyroxine are commonly dispensed — Eutroxsig, Eltroxin and Oroxine. The Therapeutic Goods Administration treats them as bioequivalent, but some patients clearly notice a difference when they switch brands. The pragmatic approach is to request the same brand at each refill where possible, and if a switch happens, recheck TSH in 6–8 weeks.

Absorption — the daily-life details that matter

Levothyroxine absorption is sensitive to timing and stomach contents. The standard advice from the Australian Medicines Handbook:

Same time daily, on an empty stomach.
Wait 30–60 minutes before food, coffee, calcium, iron, antacids, proton pump inhibitors, soy products, or multivitamins.
Coffee and calcium are the two biggest practical absorption blockers — a calcium-fortified breakfast cereal with milk can knock out a meaningful fraction of the dose.
A bedtime dose at least 3 hours after the evening meal is an alternative if morning timing is unreliable.

When the bloods are normal but symptoms persist

About one in ten people on adequate levothyroxine still report ongoing fatigue, brain fog, weight or mood symptoms despite a normal TSH. This is the integrative-curious gap — and it deserves honest naming.

The first step is not to assume the medication is wrong. The first step is to look more widely:

Adherence and timing — taken on an empty stomach, separated from coffee and calcium, consistent brand.
Iron and ferritin (low iron is common in women with heavy menstrual loss and amplifies thyroid-style fatigue).
Vitamin B12 and vitamin D — both often low in autoimmune disease.
Coeliac screen (anti-TTG-IgA) — strong autoimmune cluster with Hashimoto’s.
Obstructive sleep apnoea screen — fragmented sleep masquerades as thyroid fatigue.
Depression, anxiety, perimenopause, and chronic stress — often the actual driver.

Only after this groundwork is combination T4/T3 therapy considered, and it is specialist territory rather than general-practice initiation. The Cochrane 2009 review of combination versus T4-alone did not show clear benefit on symptoms or quality of life across the pooled trials. Desiccated thyroid extract (Armour, NDT) is not on the Australian Register of Therapeutic Goods per the TGA — supply is variable, T3:T4 ratios are non-physiological, and routine use is not supported by Australian primary-tier guidance.

The body’s not broken. The gland is producing less of one hormone than it should, and replacing it precisely — at the right dose, taken at the right time, in the right body context — is what works for the great majority of people. The harder questions are the ones around it: iron stores, sleep, mood, perimenopause, life load.

D. Australian operations

The Australian general-practice workflow for hypothyroidism is well covered by the existing MBS and PBS pathways:

Pathology — TSH, free T4, anti-TPO and anti-Tg antibodies are all bulk-billable items on the Medicare Benefits Schedule when clinically indicated. Most pathology providers automatically reflex-test free T4 when TSH is out of range, which means a single thyroid request usually returns the information needed.
PBS — levothyroxine (Eutroxsig, Eltroxin, Oroxine) is general-schedule, no authority required, in 50, 75, 100, and 200 mcg strengths. Liothyronine (Tertroxin) is on the general schedule but rarely used, and is typically specialist-initiated. Desiccated thyroid is not on the ARTG.
Chronic disease management — isolated, well-controlled hypothyroidism doesn’t usually meet the complexity threshold for a GP Chronic Conditions Management Plan, but it commonly comes alongside other chronic conditions (type 2 diabetes, dyslipidaemia, depression, atrial fibrillation) where one is appropriate.
Aboriginal and Torres Strait Islander adults — prevalence is broadly similar but access to ongoing monitoring is the bigger issue. ATSI Health Assessment items support proactive review.
Telehealth — long-established existing-relationship rules apply. Pathology-only follow-ups (a TSH check after a dose adjustment) are well suited to a quick telehealth consult.

(MBS / PBS items verified 2026-05-21 via WebSearch — workspace egress to mbsonline.gov.au + pbs.gov.au still blocked; spot-check confirms current.)

Patient-facing references most relevant in Australia are the Endocrine Society of Australia, the Australian Thyroid Foundation, HealthDirect and the Better Health Channel.

E. Special populations

Pregnancy and preconception

This is the highest-stakes scenario in general practice. The Endocrine Society of Australia and the ATA 2017 guideline, echoed in Queensland Health’s pregnancy thyroid pathway, set a preconception TSH below 2.5 and tighter trimester-specific targets:

First trimester: TSH ≤2.5
Second trimester: TSH ≤3.0
Third trimester: TSH ≤3.0–3.5

The mechanics in practice:

As soon as pregnancy is confirmed, increase the levothyroxine dose by 25–30% (a common practical rule is to take two extra tablets per week).
Recheck TSH every 4 weeks through the first trimester, then less often if stable.
Postpartum, the dose typically returns to pre-pregnancy levels — recheck TSH at 6 weeks postnatal.

Untreated or under-treated maternal hypothyroidism in early pregnancy has documented obstetric and fetal neurodevelopmental implications, which is why this is one of the few areas where general practitioners are encouraged to act fast and document the conversation carefully.

Older adults

Start low, go slow. Start at 25 mcg/day (sometimes 12.5 mcg/day if there is ischaemic heart disease), titrate every 4–6 weeks, and accept a slightly higher TSH target (up to around 6) to avoid over-replacement — over-treatment in this group meaningfully increases atrial fibrillation and osteoporotic fracture risk.

Hashimoto’s thyroiditis — ongoing monitoring

Hashimoto’s clusters with other autoimmune disease — type 1 diabetes, coeliac, vitiligo, Addison’s, and pernicious anaemia. If a new autoimmune-flavoured symptom appears (unexplained weight loss, postural dizziness, dark skin pigmentation, persistent gut symptoms, anaemia) it is worth a broader workup rather than assuming it’s the thyroid.

The T3 / NDT space

This is the area where patients arrive with questions from podcasts, online groups and overseas clinics. The honest Australian framing is:

T3 (liothyronine, Tertroxin) is on the PBS general schedule but is generally specialist-initiated in endocrinology, after a careful trial of optimised T4 monotherapy and a workup for other contributors. It is not a first-line option in general practice.
Desiccated thyroid (Armour, NDT) is not on the ARTG, supply is unreliable, and Australian primary-tier guidance does not support routine use. Some patients access it via specialist compounding pharmacies — this is a specialist conversation, not a general-practice substitution.

This is not a moral judgement on patients who feel better on T3 or NDT. It is naming where the Australian evidence and regulatory framework currently sit. The body is not failing — the gland is under-producing, and replacement is the lever. Other levers — iron, sleep, mood, stress, perimenopausal hormone changes — usually need attention before the medication is the right thing to change.

Perimenopause overlap

In women in their 40s and 50s, perimenopause symptoms — fatigue, weight changes, brain fog, mood shifts, temperature dysregulation, sleep disruption — overlap almost completely with hypothyroidism symptoms. Both diagnoses commonly co-exist. A normal TSH does not rule out perimenopause; an abnormal TSH does not mean perimenopause isn’t also contributing. A careful general-practice conversation, rather than a single blood test, is what untangles this.

When to escalate / endocrinology referral

Most hypothyroidism is well managed in general practice. Endocrinology referral is reasonable when:

TSH is normal but free T4 is low (suggesting central / pituitary hypothyroidism — needs pituitary workup).
Symptoms persist despite stable, biochemically optimised levothyroxine and a thorough workup for other contributors.
Pregnancy with unstable TSH or pre-existing complex thyroid disease.
Thyroid nodule found on examination or imaging.
Recurrent or unexplained biochemical instability.
Suspected combined adrenal and thyroid disease — autoimmune Addison’s requires steroid replacement before high-dose thyroxine to avoid precipitating adrenal crisis.
Patient interested in T3 or NDT — discussion of these options sits in endocrinology.
Paediatric hypothyroidism — paediatric endocrinology.

Acute red flags that warrant emergency review rather than referral letters include severe hypothyroidism with reduced level of consciousness, hypothermia and bradycardia (myxoedema coma — rare but high-mortality) and severe new chest pain or heart failure after starting or increasing levothyroxine.

What this article is and is not

This is general health information drawn from current Australian primary-care guidelines — Therapeutic Guidelines, the Australian Medicines Handbook, NPS MedicineWise, the RACGP, the Endocrine Society of Australia, NHMRC and the Australian Thyroid Foundation — alongside major international trials where Australian primary-tier guidance is silent (TRUST, IEMO80+, TABLET, ATA 2017 pregnancy guideline, Cochrane reviews on T4/T3 combination and selenium). It is not personal medical advice and does not create a doctor–patient relationship. Decisions about whether to test, treat, or change levothyroxine dose are made with your own general practitioner.

For Australian consumer-friendly sources: HealthDirect — Hypothyroidism, Better Health Channel — Thyroid gland, Australian Thyroid Foundation, Endocrine Society of Australia.

Sources cited

Frequently asked questions

I feel awful but my GP says my thyroid is normal — what's going on?

A normal TSH doesn't always mean nothing is wrong — it means the thyroid axis itself looks balanced on that particular test. Fatigue, weight changes, brain fog, low mood, cold intolerance and dry skin overlap with many other conditions: iron or vitamin B12 deficiency, vitamin D deficiency, sleep apnoea, depression, perimenopause, coeliac disease, chronic stress, and poor sleep. About 10% of people on adequate levothyroxine still report ongoing symptoms despite biochemically normal results. The next step is rarely 'more thyroid medication' — it's usually a broader workup. Discuss with your GP before changing or stopping levothyroxine.
What's subclinical hypothyroidism and do I need treatment?

Subclinical hypothyroidism means TSH is mildly raised (usually 4–10) but free T4 is still in the normal range. Whether to treat depends on the TSH level, symptoms, antibody status, age, and pregnancy plans. The Endocrine Society of Australia and Therapeutic Guidelines suggest treating when TSH is ≥10, when there's pregnancy or pregnancy planning, when thyroid antibodies are positive with symptoms, or when there's a goitre. For mildly raised TSH in older adults without symptoms, two major trials (TRUST and IEMO80+) showed no quality-of-life benefit from starting levothyroxine. Often the right plan is to recheck in 1–3 months — about 30% normalise without treatment.
How should I take levothyroxine for it to work properly?

Levothyroxine absorption is sensitive to timing and what's in your stomach. The standard approach is one tablet at the same time daily on an empty stomach, then wait at least 30–60 minutes before eating, drinking coffee, taking calcium, iron, multivitamins, antacids or proton pump inhibitors. Coffee and calcium are the two biggest practical absorption blockers. A bedtime dose at least 3 hours after the evening meal is an alternative if morning timing doesn't work. Brand consistency matters — Eutroxsig, Eltroxin and Oroxine are treated by the TGA as bioequivalent but some people notice a difference when brands switch, so request the same brand at each refill where possible.
I'm planning pregnancy — do I need to change my dose?

Yes — preconception planning matters more than most people realise. The Endocrine Society of Australia and the international ATA guidelines suggest a preconception TSH below 2.5 mIU/L. Once pregnancy is confirmed, the levothyroxine dose typically needs to go up by 25–30% almost immediately, with TSH checked monthly through the first half of pregnancy. The reason is that maternal thyroxine demand jumps in early pregnancy, and adequate maternal thyroid hormone matters for fetal brain development in the first trimester. If you're on levothyroxine and trying to conceive, book a preconception review — your GP will usually re-check TSH and plan the dose-increase strategy in advance.
Do I have to take a tablet forever? Are there natural alternatives?

For Hashimoto's and most other causes of established overt hypothyroidism, yes — the gland's hormone-making capacity has been damaged and won't return. Levothyroxine isn't a drug in the typical sense; it's the same molecule (T4) the body normally makes. Combination T4/T3 therapy and desiccated thyroid (Armour, NDT) sit in a more complicated space — Cochrane reviews have not shown clear benefit over T4 alone, desiccated products are not on the Australian Register of Therapeutic Goods, and where T3 is used it's generally specialist-initiated. The body isn't broken; the gland is just under-producing one hormone, and replacing it precisely is what the medication does. Address absorption, brand consistency, and the other contributors to fatigue before assuming the medication is the problem.
What about iodine, selenium, and supplements for Hashimoto's?

Iodine: Australia has had mandatory iodine fortification of bread since 2009 and most adults don't need supplemental iodine. Pregnant and breastfeeding women are an exception — the NHMRC recommends 150 mcg/day in pregnancy and lactation. Mega-dose iodine (kelp, seaweed supplements) can actually trigger or worsen autoimmune thyroiditis and is best avoided. Selenium: there is modest evidence (small randomised trials and a Cochrane review) that 100–200 mcg/day selenium may reduce anti-TPO antibody titres in Hashimoto's, though clinical benefit is uncertain — a time-limited trial is reasonable but watch for selenosis at high doses. Vitamin D and iron deficiency are common in autoimmune disease and worth correcting if low. None of these replace levothyroxine when it's indicated.

Source quality

Sources grouped by evidence tier. AU primary tier first; international where AU is silent or lagging; named-author reconstruction where guidelines have not yet caught up. How tiers work.