Hypothyroidism
Red Flags
| Red flag | Why dangerous | Action |
|---|---|---|
| Hypothermia + confusion + bradycardia + hypoventilation in known or suspected hypothyroidism | Myxoedema coma — life-threatening emergency. Mortality 25–60% even with treatment. Precipitated by cold exposure, infection, opioids, or sedatives in severely hypothyroid patient. | 999 immediately |
| New hypothyroidism discovered in pregnancy or patient trying to conceive | Untreated hypothyroidism in pregnancy: miscarriage, pre-eclampsia, stillbirth, foetal neurodevelopmental impairment (irreversible). Urgency is disproportionate to TSH level — even mild elevation is dangerous. | Same-day urgent obstetric referral |
| Rapidly enlarging goitre or asymmetric thyroid swelling with hypothyroidism | While most goitres with hypothyroidism are Hashimoto's, rapidly enlarging or asymmetric swellings must exclude thyroid malignancy. Anaplastic thyroid cancer can present with rapid growth and hypothyroidism. | Urgent 2WW thyroid cancer referral |
| Severe symptomatic hypothyroidism with cardiac complications (pericardial effusion, bradycardia, cardiac failure) | Severe hypothyroidism can cause pericardial effusion, dilated cardiomyopathy, and profound bradycardia. Too-rapid levothyroxine replacement in this context can precipitate arrhythmia — requires hospital initiation. | Urgent cardiology review before starting levothyroxine |
- Not asking about pregnancy/fertility — critical omission in a woman of childbearing age with new hypothyroidism
- Not asking about calcium/iron/PPI — missing the most important levothyroxine interaction
- Not addressing the antidepressant started without TFTs — must acknowledge and plan
999 or Same-Day Specialist
Act now- Myxoedema comaHypothermia + confusion + bradycardia + hypoventilation → 999; IV T4; ITU; mortality 25–60%
- Hypothyroidism in pregnancy or trying to conceiveSame-day obstetric referral; start levothyroxine immediately; TSH target <2.5 (1st trimester)
- Severe hypothyroidism with cardiac complicationsPericardial effusion, bradycardia, cardiac failure → urgent cardiology review before initiating levothyroxine (too-rapid replacement precipitates arrhythmia)
- Rapidly enlarging or asymmetric goitre2WW thyroid cancer referral — exclude anaplastic carcinoma
Endocrine Referral
Weeks- Symptoms persist despite TSH in target range on adequate levothyroxine doseConsider T3/T4 combination (controversial; specialist decision only). Exclude poor absorption, adherence, interactions.
- Elderly/frail with significant cardiac historyStart 25 mcg levothyroxine with cardiology involvement; very slow titration
- Drug-induced hypothyroidism (amiodarone, lithium)Coordinate with the prescribing team; do not stop amiodarone without cardiology input
- MEN2 or other hereditary thyroid syndrome suspectedGenetic counselling and specialist endocrine assessment
Primary Care Management
GP practice- Overt hypothyroidism (TSH >10, low free T4, symptoms) in otherwise well adultStart levothyroxine 50 mcg OD; recheck TSH + free T4 at 6–8 weeks; titrate in 25 mcg increments
- Subclinical hypothyroidism (TSH 4–10, normal free T4) with symptoms or TPO antibodiesIndividualise; if treating, start 25–50 mcg OD; review TSH at 6 weeks; annual monitoring if not treating
- Known hypothyroidism on stable levothyroxine — annual reviewAnnual TFTs; review dose if weight change, pregnancy status, or new drug interactions
- Post-thyroidectomy replacement therapyLifelong levothyroxine; TSH target depends on cancer status (suppressed for thyroid cancer; normal range for benign)
- Not recognising pregnancy/fertility as an urgent escalation trigger
- Starting levothyroxine in an elderly cardiac patient at 50 mcg without specialist input
- Not recognising myxoedema features as a 999 emergency
- Not examining the thyroid in a patient with hypothyroid symptoms — missing goitre, nodule, or malignancy signs
- Not checking cardiovascular status before starting levothyroxine in an elderly or cardiac patient
- Ordering free T3 as a first-line investigation — not routine in primary care hypothyroidism
- Not checking lipids — hypothyroidism-related hypercholesterolaemia should be documented before considering statins
"Your blood tests confirm that your thyroid gland is underactive. The thyroid is like the body's thermostat — it controls how fast your metabolism runs. When it's underactive, everything slows down: your energy, your digestion, your ability to keep warm, your mood, and even your thinking. This explains every symptom you've been having — the fatigue, weight gain, constipation, feeling cold, hair thinning, and the low mood. Importantly, this is not depression — or at least not the primary cause. I think the antidepressant you were started on recently may not have been the right first step, because the root cause is the thyroid. The good news is that this is very treatable with a simple tablet called levothyroxine — it replaces the hormone your thyroid should be making. Once your thyroid levels are right, most of your symptoms should improve significantly over the next 3 to 6 months."
"Will I have to take this tablet forever?"
"Most people with autoimmune hypothyroidism — which is what this appears to be — do need to take it long-term. The good news is that it's a simple once-daily tablet with very few side effects when the dose is right, and many people feel dramatically better once they're on the right dose. We'll monitor your blood tests regularly to make sure we keep it optimised."
"Will the weight come off once I start the tablet?"
"It often does improve — you may lose 2–3 kg once your metabolism returns to normal. However, I want to be honest: the thyroid replacement usually helps with the metabolic component, but if other factors like diet and activity are contributing, those will still need attention. I don't want to promise a transformation that isn't certain — but the metabolic contribution from the thyroid should improve."
"What about the antidepressant — should I stop it?"
"I wouldn't stop it abruptly without a plan — that needs careful thought. Once your thyroid levels are treated and normalised, we can review your mood again and decide together whether the sertraline is still needed. Many people find that their mood improves significantly with the thyroid treatment alone. Let's give it 3 months and see."
Hashimoto's thyroiditis (autoimmune)
Most common cause (70–80%). TPO antibodies positive. May fluctuate. Associated with other autoimmune conditions. Lifelong levothyroxine in most cases.
Post-thyroidectomy or post-radioiodine
Iatrogenic — lifelong replacement mandatory. Dose requirements may change with age. TSH target depends on indication (suppressed if thyroid cancer, normal range for benign).
Iodine deficiency (rare in UK)
Endemic hypothyroidism from dietary iodine deficiency. More common in pregnancy and in populations avoiding iodised salt and dairy. Resolves with adequate iodine.
Amiodarone-induced hypothyroidism
TSH elevation in patient on amiodarone (37% iodine). Do NOT stop amiodarone without cardiology — can precipitate life-threatening arrhythmia. Levothyroxine prescribed alongside.
Lithium-induced hypothyroidism
Up to 40% of long-term lithium users develop hypothyroidism. Coordinate with psychiatry before modifying lithium. Levothyroxine prescribed alongside ongoing lithium in most cases.
Subclinical hypothyroidism (TSH 4–10)
Individualise treatment — consider symptoms, TPO antibodies, age, pregnancy plans. Two elevated TSH results required before treatment. Annual TSH if not treating.
Myxoedema coma
Severe hypothyroidism + hypothermia + confusion + bradycardia. 999. IV levothyroxine. ITU. Mortality 25–60%. Precipitants: cold exposure, infection, opioids.
Hypothyroidism in pregnancy
Any elevation in TSH in pregnancy. Urgent obstetric referral. Levothyroxine immediately. TSH target <2.5 in first trimester. Foetal neurodevelopment at risk.
- Not addressing the antidepressant started without TFTs — needs acknowledgement and plan
- Promising complete weight normalisation — overpromising leads to loss of therapeutic trust
- Not checking understanding after explanation
Validate — name their expectation
Most patients expect to start a tablet and feel better quickly. Many are also frustrated that the antidepressant was started without checking the thyroid. Both of these expectations deserve direct acknowledgement before the clinical plan.
"You've been struggling for months and I completely understand the frustration — particularly that this wasn't picked up earlier. I want to put that right today."Explain — share your clinical reasoning
The response to levothyroxine is gradual — symptoms improve over 3–6 months, not days. Setting this expectation prevents premature dose escalation based on ongoing symptoms. The thermostat analogy explains why it takes time: the body needs to readjust all its systems to a higher metabolic rate.
"The tablet works by gradually turning up the thermostat — your body has been running slow for months and it takes time for everything to recalibrate. Most people start feeling better within 4–6 weeks, but the full benefit takes 3–6 months."Negotiate — offer something concrete today
Give the prescription today with specific counselling on timing. Book the 6–8 week blood test appointment before the patient leaves. Address the calcium interaction immediately — this is actionable today and prevents treatment failure.
"I'm going to prescribe this today — and the most important thing about taking it correctly is timing: take it on an empty stomach, 30 minutes before breakfast, and your calcium tablet at a completely different time — lunchtime or evening. I'm booking your blood test for 6 weeks."Levothyroxine absorption is significantly reduced by food (particularly high-fibre and calcium-rich foods), coffee, and certain medications. An empty stomach maximises absorption. Consistency of timing improves TSH stability and reduces dose variation.
Take levothyroxine first thing in the morning — before getting up if possible — with a full glass of water. Wait 30 minutes before breakfast. Set a phone alarm if helpful. Bedtime dosing is an evidence-based alternative for those who cannot take it fasting in the morning.
Calcium carbonate, calcium citrate, ferrous sulphate/fumarate, and PPIs (especially omeprazole) all reduce levothyroxine absorption by 20–40%. Cholestyramine, sucralfate, and antacids also interfere. This is the most common cause of apparent treatment failure in primary care.
This patient takes calcium carbonate daily. Specific instruction: levothyroxine at 7am before breakfast; calcium carbonate with lunch or at bedtime — minimum 4 hours apart. Write this down for the patient and document it in the notes as a counselling point.
Iodine is required for thyroid hormone synthesis. In the UK, iodine deficiency is rare but emerging (particularly in vegans who avoid dairy). Excessive iodine supplementation (seaweed, high-dose iodine supplements) can paradoxically worsen Hashimoto's by triggering immune activation (Wolff-Chaikoff effect).
Normal UK diet with dairy provides adequate iodine. Vegetarians/vegans: consider iodine-fortified foods or low-dose supplement (150 mcg/day — not kelp-based which has variable high iodine content). Avoid high-dose iodine supplements entirely in Hashimoto's.
Hypothyroidism reduces cardiac output and muscle metabolism, making vigorous exercise difficult. During the titration period, gentle consistent activity (walking, swimming) maintains cardiovascular fitness and mental wellbeing without overloading an underperforming cardiac system.
Start with 20–30 minute daily walks; build up as energy improves. Avoid pushing through severe fatigue — this is physiological, not lack of effort. As TSH normalises, energy and exercise tolerance typically improve significantly.
Hypothyroid-driven depression typically improves with thyroid treatment alone. However, it may take 3–6 months to resolve fully. If mood is not improving at 3 months despite TSH in target range, primary depression may be coexisting and antidepressant review is warranted.
PHQ-9 at each review. Do not abruptly stop the sertraline — review at 3-month thyroid check. If TSH is now normal and mood is not improving: maintain antidepressant. If TSH is normal and mood is significantly better: discuss tapering plan. Never stop sertraline abruptly.
Foetal thyroid function is not established until 16–20 weeks of gestation. Before this, the foetus is entirely dependent on maternal T4 for neurodevelopment. Even mild maternal hypothyroidism in the first trimester causes irreversible foetal neurological impairment.
This patient is trying to conceive: optimise TSH to <2.5 before conception. When pregnancy test is positive: increase levothyroxine dose by 25–30% immediately (add 2 extra doses per week is a practical rule), recheck TSH in 4 weeks. Refer to obstetric endocrinology at booking appointment.
Levothyroxine 50 mcg OD — fasting, 30 min before breakfast
- Start 50 mcg OD; recheck TSH + free T4 at 6–8 weeks
- If TSH still elevated: increase by 25 mcg; recheck at 6–8 weeks
- Continue in 25 mcg steps until TSH in target range (0.5–2.5 mU/L)
- Most adults require 75–150 mcg/day at maintenance
- Target: TSH in lower half of normal range for symptom relief
Levothyroxine 25 mcg OD — very slow titration
- Start 25 mcg OD; increase by 25 mcg every 4–6 weeks
- ECG before initiation in significant cardiac disease
- Too-rapid replacement precipitates angina, arrhythmia, or cardiac failure
- Accept a higher TSH (3–6 mU/L) if cardiac stability requires it
- Cardiology input if significant IHD, LV impairment, or arrhythmia history
Levothyroxine — start immediately; urgent titration
- TSH <2.5 mU/L in 1st trimester — more urgent target than general population
- Start 50–75 mcg OD; recheck TSH in 4 weeks (not 6–8 weeks — more urgent)
- When pregnancy confirmed: increase dose by 25–30% immediately (add 2 extra doses/week)
- TSH targets: 1st trimester <2.5; 2nd/3rd trimester <3.0
- Post-partum: reduce back to pre-pregnancy dose; recheck TSH at 6 weeks post-partum
- Poor adherence: Most common cause — missed doses; irregular timing; never changed behaviour from "as needed" mental model
- Drug interaction (calcium, iron, PPI, cholestyramine): Reduces absorption by 20–40%; correct timing before escalating dose
- Malabsorption: Coeliac disease (check anti-tTG), inflammatory bowel disease, or bowel resection — switch to liquid levothyroxine or soft-gel capsule formulation
- Dose too low for body weight: Recalculate target dose (~1.6 mcg/kg ideal body weight)
- Other causes of elevated TSH: Non-compliance, recent acute illness (TSH transiently rises), assay interference (biotin supplementation falsely lowers TSH in some assays)
- Review TSH target: Aim for lower half of normal range (0.5–2.0 mU/L) — some patients feel better with a lower-normal TSH
- Check free T4: Should be in mid-normal to upper-normal range; if low-normal TSH with low-normal T4, patient may be relatively under-replaced
- Exclude other causes: Anaemia, coeliac disease, depression, fibromyalgia, sleep apnoea — all produce similar symptoms
- T3/T4 combination: Controversial; not routinely recommended in NICE or BTA guidelines; specialist decision only; has cardiac risk (T3 has shorter half-life, harder to titrate safely)
- Endocrinology referral: If TSH consistently in range and symptoms persist after thorough primary care review
Select patient characteristics — review levothyroxine dosing considerations below
"Take this tablet first thing in the morning on an empty stomach — before eating or drinking anything except water. Wait at least 30 minutes before breakfast. Your calcium tablet should be taken at least 4 hours later — lunchtime works perfectly. It's very important to be consistent about timing — taking it at different times each day makes it harder to know if the dose is right."
In SCA: the two most important levothyroxine counselling points are (1) fasting administration 30 min before food and (2) 4-hour separation from calcium/iron/PPIs. Both earn Tasks marks. Also: never titrate by symptoms alone — TSH must be rechecked at 6–8 weeks. For pregnancy: increase dose by 25–30% immediately on positive test.
"This is the active form of thyroid hormone — it works more quickly than the levothyroxine but also wears off more quickly. You'll take it twice a day. It's very important that your blood tests are checked regularly because getting the dose exactly right is more difficult with this medication."
In SCA: key knowledge points — T3 is NOT initiated in primary care; persistent symptoms on adequate T4 require other cause exclusion first; T3 has cardiac risk; NICE does not routinely recommend T3/T4 combination. Demonstrating this knowledge gains a Tasks mark.
"Your thyroid is in what we call the 'borderline' range — the body is working harder than it should to maintain normal thyroid levels. Given your symptoms and the antibody result, I think it's worth trying a low-dose thyroid tablet to see if it helps. We'll review in 6 weeks and if you feel better and the blood test improves, we'll continue."
In SCA: the subclinical hypothyroidism decision framework is a key knowledge point. TSH >10: always treat. TSH 4–10: individualise based on symptoms, TPO antibodies, age, pregnancy. Two samples before treating. Annual monitoring if not treating. Demonstrating this nuance gains a Tasks mark.
"The cause of your underactive thyroid is your immune system producing antibodies that gradually slow down the thyroid — this is very common, and it's not your fault or anything you did. It does mean it's a lifelong condition in most cases, but one that we can manage very effectively with the right tablet dose. It also means we should keep an eye on a few other autoimmune conditions that can sometimes occur alongside this one — I'll check a couple of additional blood tests today."
In SCA: identifying Hashimoto's means screening for associated autoimmune conditions (coeliac, type 1 diabetes, B12 deficiency) and counselling about the autoimmune nature and the family risk. These are specific Tasks marks available in this scenario.
Myxoedema coma is unlikely to be the SCA scenario itself but may appear in the stem as a case that "was initially treated as sepsis" or "presented with confusion." Recognising the combination of hypothermia + confusion + bradycardia in a patient with known hypothyroidism (or with classic signs) is the key knowledge point.
In SCA: myxoedema coma is an emergency — 999 is the answer, not "urgent referral to endocrine outpatients." The mortality rate (25–60%) and the precipitants (cold, infection, opioids) are specific knowledge points that gain Tasks marks.
"Before your baby can make its own thyroid hormone — which doesn't happen until 16 weeks — it completely relies on yours. Getting your thyroid levels right is one of the most important things we can do for your baby's brain development. We need to act on this quickly and keep checking your levels every month during the pregnancy."
In SCA: hypothyroidism in pregnancy is one of the highest-stakes clinical scenarios — the urgency (same-day action, not routine management) and the specific TSH target (<2.5 in 1st trimester) are both examined knowledge points. Failing to recognise the urgency is a Tasks domain failure.
Work and Cognitive Function
Cognitive slowing, poor concentration, and memory difficulties from hypothyroidism significantly impair work performance — particularly in cognitively demanding roles. Teachers, managers, and professionals often experience a progressive decline in performance they attribute to "burning out."
A fit note is a legitimate and compassionate option for patients with severe symptomatic hypothyroidism during the titration period — particularly if the patient is a teacher managing 30 children while profoundly hypothyroid.
Framing the cognitive improvement as expected — "your thinking will improve as the levels come right" — provides hope and a concrete endpoint.
"A lot of the difficulty you've been having at work — the tiredness, difficulty concentrating — these are very likely to improve significantly as your thyroid levels come up to normal. It's the thyroid, not you."Weight and Body Image
Weight gain from hypothyroidism is frequently catastrophised by patients as "I've lost control" — and just as frequently dismissed by clinicians as "lifestyle." Reframing weight gain as a direct metabolic consequence of thyroid failure is one of the most important and restorative things a GP can do in this consultation.
However, honest expectation management is equally important: levothyroxine typically reduces hypothyroid-related weight by 2–5 kg. It does not produce dramatic weight loss if other factors are contributing.
Patients who expect complete weight normalisation and do not achieve it may lose faith in the treatment — and in themselves. Set a realistic, honest expectation.
"The weight gain you've experienced is a direct consequence of your thyroid slowing your metabolism down — it is not your fault. Most people lose 2–3 kg once the thyroid is treated, but I want to be honest that it's not a complete fix for weight."Depression and Misdiagnosis
In this case, the patient was started on an antidepressant without TFTs being checked — a common and consequential error in primary care. Addressing this sensitively without undermining the previous GP or causing the patient to lose confidence in primary care as a whole is a clinically challenging communication task.
Frame it as "a new finding that changes the picture" rather than "a mistake that was made." This is not dishonest — it is exactly what has happened: new information has become available.
The antidepressant (sertraline) should not be stopped abruptly. Plan a review at 3 months — if mood has improved with thyroid treatment, a supervised taper can be planned at that point.
"I want to be honest — I think your thyroid is the primary driver of your low mood. We should treat that first and then review whether the antidepressant is still needed at 3 months. We won't stop it suddenly."Relationships and Intimacy
Hypothyroid fatigue, low libido, and mood changes place significant strain on intimate relationships. Partners may interpret the patient's withdrawal, low energy, and emotional flattening as loss of interest or depression — creating relationship conflict on top of an undiagnosed illness.
After diagnosis, some patients and partners benefit from a simple explanation of what hypothyroidism does to energy, mood, and libido — and realistic reassurance that these changes are typically reversible with treatment.
Low libido from hypothyroidism should not be attributed to relationship problems without biochemical investigation. TSH should be one of the first tests in any patient presenting with new reduced libido or sexual dysfunction.
"Some of the changes you've noticed in your energy and mood — and in how you've been in your relationship — are very likely to improve as the thyroid treatment takes effect. It can take a few months, but the improvement is often quite marked."Fertility and Preconception
In this case, the patient is trying to conceive. Untreated hypothyroidism causes anovulatory cycles, menorrhagia, and increased miscarriage risk. The TSH must be optimised to <2.5 before conception — this is the most urgent priority in this consultation.
Framing this positively — "treating the thyroid significantly improves the chances of a successful pregnancy" — is honest and motivating. This is not a minor incidental finding; it is the single most clinically important aspect of the management plan for this patient.
Refer to obstetric endocrinology simultaneously with starting treatment — do not wait until pregnant to involve the specialist team.
"Treating your thyroid will significantly improve your chances of getting pregnant and having a healthy pregnancy. This is the most important thing we can do for you right now, and I want to act on it today."Lifelong Medication Anxiety
Many patients are anxious about committing to lifelong daily medication. Hashimoto's hypothyroidism is almost always permanent — this is a lifelong condition requiring lifelong treatment. Normalising this honestly ("it's similar to taking a blood pressure tablet or vitamin D — it becomes part of your daily routine") reduces anxiety.
Emphasising the simplicity of the regimen — one tablet daily, inexpensive, well-tolerated when dose is right — contrasts with the complexity of managing the undiagnosed condition (multiple GP visits, antidepressants, investigations for individual symptoms).
Address the fear of side effects directly: levothyroxine is bio-identical to the body's own T4 — when the dose is correct, there are essentially no side effects beyond the consequences of over-replacement (dose too high).
"This tablet is replacing something your body needs but isn't making enough of — it's bio-identical to your own hormone. When the dose is right, most people have no side effects at all. It becomes as simple as taking a vitamin every morning."6–8 weeks — First dose response check
TSH + free T4. If TSH still above target: increase levothyroxine by 25 mcg; rebook in 6–8 weeks. If TSH in range: symptoms assessment — are they improving? If TSH low/suppressed: dose too high — reduce by 25 mcg; recheck. Review calcium interaction counselling. For this patient (TTC): check if pregnant — if so, increase dose by 25–30% immediately and refer to obstetric endocrinology urgently.
3 months — Symptom and mood review
Review all hypothyroid symptoms: fatigue, weight, mood, constipation, hair loss, cold intolerance. PHQ-9 for mood. If TSH in range and mood improving: plan sertraline taper supervised. If TSH in range and mood not improving: primary depression likely coexisting — continue antidepressant; review diagnosis. Recheck TSH if dose changed at 6-week appointment.
6 months — TSH stable confirmation
TSH + free T4. If stable and symptoms resolved: confirm maintenance dose; move to annual monitoring. Recheck cholesterol if elevated at diagnosis — typically normalises at 6 months once euthyroid. If symptoms persist despite TSH in range: screen for coeliac disease, B12, anaemia, sleep apnoea; review diagnosis; consider endocrinology referral if all excluded.
Annual — stable hypothyroidism review
Annual TSH ± free T4 (free T4 needed if TSH in range but symptoms). Dose review — requirements change with age, weight change (>10% change warrants dose recalculation), new medications (especially amiodarone, antiepileptics), menopause, and pregnancy. Annual review of associated autoimmune conditions in Hashimoto's. Hashimoto's: TPO antibodies do not need annual retesting — if positive at diagnosis, remains positive.
Pregnancy — every 4 weeks in 1st 20 weeks
For this patient, once pregnant: TSH every 4 weeks for first 20 weeks of pregnancy; then once per trimester. Increase levothyroxine dose by 25–30% immediately on positive pregnancy test. Refer to obstetric endocrinology at booking. Post-partum: reduce dose to pre-pregnancy level; recheck TSH at 6 weeks post-partum; check TSH at 3 and 6 months for post-partum thyroiditis (particularly in Hashimoto's).
Memory rule
Start 50 mcg OD (25 mcg elderly/cardiac); recheck TSH at 6–8 weeks; titrate in 25 mcg steps; target TSH 0.5–2.5 mU/L; never titrate by symptoms alone; separate from calcium/iron/PPIs by 4 hours minimum. Pregnancy: TSH target <2.5 (1st trimester); recheck every 4 weeks; increase dose 25–30% on positive test immediately. Annual TSH when stable.
⚠ Three scenario-specific safety-net phrases
Why safety-netting matters beyond clinical care
- Calcium interaction not counselled — the most important practical instruction in this consultation
- Pregnancy protocol not given — for a patient TTC, this is a critical safety-net omission
- Sertraline stopped immediately or abruptly — never abrupt cessation; review planned
- Starting at 50 mcg in an elderly or cardiac patient without ECG or slow titration plan
- Promising complete weight and mood resolution — overpromising damages therapeutic trust
- Closing question absent
- TSH + free T4 + TPO antibodies ordered
- Levothyroxine 50 mcg prescribed with correct timing instruction (fasting, 30 min before food)
- Calcium interaction counselled — minimum 4 hours apart
- Pregnancy protocol given — call same day; dose increase immediately
- Sertraline reviewed with clear plan (not stopped; review at 3 months)
- 6–8 week follow-up TSH booked before patient leaves
- Myxoedema safety-net for emergency features
- Thermostat analogy used — all symptoms linked to one cause
- Antidepressant addressed sensitively — "new finding changes the picture," not "previous GP made an error"
- Weight expectations managed honestly — partial improvement, not complete resolution
- Fertility urgency communicated without causing panic
- Lifelong medication concern addressed — reframed as simple daily habit
- Understanding checked; closing question asked
Who you are
Sarah Brennan, 42 years old, secondary school teacher. 4-month history of progressive fatigue (sleeping 9–10 hours, still exhausted), 5 kg weight gain with no dietary change, feeling cold even in a warm classroom, constipation (every 3–4 days), hair thinning (particularly the front hairline and eyebrows), dry skin, low mood and difficulty concentrating. Started sertraline 50 mg 3 weeks ago by a locum GP who did not check TFTs. Takes calcium carbonate 500 mg daily for osteoporosis prevention advice from a sports physio. No cardiac history. Not pregnant but actively trying to conceive with her partner for 6 months. No family history of thyroid disease that she knows of. Non-smoker. BMI 27.
Hidden agenda
Two main concerns: (1) She is trying to conceive and has been told by her partner that "the antidepressant might affect fertility." She is worried but has not been told why the antidepressant was started or what to expect. She will not volunteer this unless specifically asked about pregnancy or fertility plans. If the GP asks and she discloses — and then receives a clear, urgent, and reassuring response ("we will sort this quickly and it significantly improves your fertility") — she becomes visibly relieved and fully engaged. (2) She suspects she has a thyroid problem because she Googled her symptoms at 2am. She is frustrated that it wasn't checked. She will not volunteer this unless asked "what do you think might be causing this?" — at which point she will say "I thought it might be my thyroid but the last GP didn't seem to think so."
Symptoms if asked directly
- Fatigue: constant, not relieved by sleep, present even on weekends when not working
- Weight: 5 kg gained over 4 months without diet change
- Cold intolerance: wears extra layers; feels cold when colleagues are comfortable
- Hair: noticeably thinner; partner has commented on it; outer third of eyebrows sparse
- Bowels: every 3–4 days, harder than usual
- Mood: flat, not quite depressed — "more like switched off"
- Voice: slightly huskier than before — first noticed it 2 months ago
- Periods: heavier than before, lasting 6–7 days (was 4)
- No palpitations, no heat intolerance, no sweating, no tremor
Bonus details
- If asked about calcium carbonate: "I take it with breakfast — does that matter?"
- If asked about family history: "Actually, now you mention it — my older sister has something wrong with her thyroid. She takes a tablet for it."
- Challenge: "The locum told me I was depressed — was she wrong? Should I stop the antidepressant?"
Resolution criteria: Sarah will accept the plan if the candidate (1) confirms the suspected thyroid diagnosis with a clear explanation using the thermostat analogy; (2) specifically addresses the calcium timing — "take levothyroxine before breakfast, calcium at lunchtime, minimum 4 hours apart"; (3) addresses fertility explicitly and urgently — "we need to get your thyroid levels right before you conceive, and once pregnant, call us immediately to increase your dose"; (4) handles the antidepressant sensitively — "review at 3 months, not stopping now"; (5) books a 6–8 week blood test; (6) asks the closing question.
- Myxoedema coma: hypothermia + confusion + bradycardia → 999
- Pregnancy / TTC: any TSH elevation → same-day start + obstetric referral
- Rapidly enlarging goitre → 2WW thyroid cancer referral
- Severe cardiac complications before starting → cardiology first
- Amiodarone-induced: never stop amiodarone; treat with levothyroxine alongside
- Elderly / cardiac: 25 mcg start; ECG; cardiology input
- Persistent symptoms on optimal T4 → endocrine referral
- Overt hypothyroidism: start 50 mcg OD; TSH at 6–8 weeks
- Subclinical TSH >10: treat regardless of symptoms
- Subclinical TSH 4–10: individualise (symptoms, TPO, age, pregnancy)
- Annual TSH when stable
| Scenario | Test | Timing | Action threshold |
|---|---|---|---|
| Any dose change | TSH + free T4 | 6–8 weeks | TSH elevated: increase 25 mcg. TSH suppressed: reduce 25 mcg. Never change dose before 6-week result. |
| Stable hypothyroidism | TSH (± free T4) | Annually | TSH outside 0.4–4.0: adjust dose. Weight change >10% or new interacting drug: recheck TSH. |
| Pregnancy | TSH + free T4 | Every 4 weeks (first 20 weeks) | TSH >2.5 (1st trimester): increase dose. Post-partum: reduce to pre-pregnancy dose; recheck at 6 weeks. |
| Subclinical, not treating | TSH + free T4 | Annually | TSH >10: treat. TSH 4–10 progressing: consider treatment. |
→ Most urgency-changing question in any woman of childbearing age with new hypothyroidism
→ Most common cause of levothyroxine treatment failure; must be timed specifically (4 hours)
→ Never abrupt cessation; plan review at 3 months when TSH normalises
→ Start 25 mcg; very slow titration; cardiology input; too-rapid replacement precipitates arrhythmia
→ Symptoms lag 6–8 weeks behind biochemical response; always recheck TSH before changing dose
→ Specialist-initiated only; not NICE/BTA recommended routinely; cardiac risk
→ Typically 2–5 kg metabolic component; honest expectation prevents loss of therapeutic trust
→ Must be explicit: "call same day on positive test; increase dose immediately"
→ "Is there anything else?" is a consistently marked RO domain item