endo.hypothyroidism.core.v1PRODUCTION

endo.hypothyroidism.core.v1

Hypothyroidism (overt / subclinical / central — standalone core)

endocrinologychronicadultgeriatricpregnancy

Hard-required inputs

0 / 10

Care setting:

Encounter flow

12/12 authored

Canonical 12-phase frame with authored status for this dossier.

Current phase

Frame

Detailed

Hypothyroidism is a biochemical state requiring a mandatory phenotype split BEFORE levothyroxine: overt primary vs subclinical vs central vs non-thyroidal illness vs transient (thyroiditis/drug). Treatment target, treat-threshold, and safety steps differ by phenotype (ATA 2014 Jonklaas)

Inputs

Actions

Advance rule

Set

Advance when

Scope set to chronic ambulatory hypothyroidism with the 5-way phenotype frame explicit

Patient inputs (13)

age*demographic • CONTEXT

Age-specific TSH reference + higher treatment threshold in elderly; oldest-old (>80–85) wait-and-see (TRUST; ETA 2013)

pregnancy_status*demographic • CONTEXT

Trimester-specific TSH targets; ~20–30% levothyroxine dose increase at confirmation; SCH treatment threshold differs (ATA 2017)

cardiac_disease*history • CONTEXT

not present

CAD / ischaemic heart disease / arrhythmia → start low (25–50 µg/day) and up-titrate slowly to avoid precipitating ischaemia/AF (ATA 2014)

pituitary_or_hypothalamic_disease*history • CONTEXT

not present

Known sellar mass / cranial RT / Sheehan / TBI raises pre-test for CENTRAL hypothyroidism — changes target organ and adrenal-first sequencing

acute_illness_status*history • CONTEXT

Acute severe illness causes non-thyroidal illness syndrome (NTIS) — defer interpretation/treatment and retest after recovery

concurrent_meds*medication • CONTEXT

not present

PPI / calcium / iron / fiber / estrogen / malabsorption alter levothyroxine absorption; amiodarone / lithium / checkpoint-inhibitor / TKI / interferon cause thyroid dysfunction

serum_tsh*lab • INITIAL_WORKUP

Primary screening + titration analyte for PRIMARY disease; uninformative for titration in central hypothyroidism

free_t4*lab • INITIAL_WORKUP

Distinguishes overt (low FT4) from subclinical (normal FT4) and is the decisive analyte in central disease (titrate FT4, not TSH)

myxedema_decompensation_features*symptom • RED_FLAGS

Hypothermia, depressed consciousness, hypoventilation, bradycardia, hyponatremia — screen for myxedema coma → escalate OUT to the acute engine

weight_kg*demographic • TREATMENT

Weight-based full replacement dosing (1.6 µg/kg/day) (ATA 2014)

tpo_antibodylab • BRANCHING_WORKUP

TPO-Ab+ identifies autoimmune (Hashimoto) aetiology and ~2× higher SCH→overt progression — drives the treat-vs-observe and pregnancy decisions

prior_thyroid_ablation_or_surgeryhistory • CONTEXT

not present

Post-thyroidectomy / post-RAI = near-certain permanent primary hypothyroidism (pre-test ≈ certainty)

cortisol_axislab • RED_FLAGS

In suspected central hypothyroidism, exclude/treat adrenal insufficiency BEFORE levothyroxine (T4 before cortisol can precipitate adrenal crisis)

* = hard-required. Engine cannot meaningfully run until these are filled.

Severity triggers (11)

11 need judgement

informationallife_threateningmyxedema_decompensation
Hypothermia + depressed consciousness + hypoventilation/bradycardia ± hyponatremia in a hypothyroid patient — myxedema coma (ATA 2014 Jonklaas)
Trigger could not be auto-evaluated — needs clinician judgement.
informationalseverecentral_hypothyroidism_adrenal_first
Low/inappropriately-normal TSH + low FT4 suggesting central disease, especially with sellar mass / cranial RT / Sheehan / TBI and possible adrenal insufficiency (ATA 2014 Jonklaas; JCEM 2014 — central CH not always mild)
Trigger could not be auto-evaluated — needs clinician judgement.
informationalseverepregnancy_or_preconception_hypothyroid
Hypothyroid (overt or subclinical, esp. TPO-Ab+) woman who is pregnant or planning pregnancy (ATA 2017 Alexander)
Trigger could not be auto-evaluated — needs clinician judgement.
informationalmoderatesubclinical_tsh_over_10
Subclinical hypothyroidism with TSH >10 mIU/L (normal FT4) (ETA 2013 Pearce)
Trigger could not be auto-evaluated — needs clinician judgement.
informationalmoderatecardiac_disease_start_low
Overt hypothyroidism requiring replacement in a patient with CAD / ischaemic heart disease / arrhythmia (ATA 2014 Jonklaas)
Trigger could not be auto-evaluated — needs clinician judgement.
informationalmoderatelevothyroxine_over_replacement
Suppressed TSH (± high-normal/high FT4) on levothyroxine — iatrogenic over-replacement (Circulation 2017; JAMA 2015)
Trigger could not be auto-evaluated — needs clinician judgement.
informationalmoderatesubclinical_progression_high_association
Subclinical hypothyroidism with BOTH a raised TSH and positive thyroid (TPO) antibodies — very high progression risk to overt disease; tighten surveillance / lower treat-threshold (Whickham 20-yr cohort)
Trigger could not be auto-evaluated — needs clinician judgement.
informationalmoderatedrug_induced_hypothyroidism
New / rising TSH on amiodarone, lithium, or an immune-checkpoint inhibitor (PD-1/PD-L1/CTLA-4) — drug-induced thyroid dysfunction; usually replace rather than stop the culprit drug (Lancet 2012; JAMA Oncol 2018; Horm Metab Res 2019)
Trigger could not be auto-evaluated — needs clinician judgement.
informationalmildelderly_mild_subclinical_observe
Age >65–70 (esp. oldest-old >80–85) with mild SCH (TSH ≤10, normal FT4) (TRUST Stott NEJM 2017; ETA 2013 Pearce)
Trigger could not be auto-evaluated — needs clinician judgement.
informationalmildpersistent_symptoms_euthyroid
Persistent hypothyroid-type symptoms despite a normal TSH on adequate levothyroxine (5–10% of patients) (2012 ETA Wiersinga; 2021 ATA/BTA/ETA consensus)
Trigger could not be auto-evaluated — needs clinician judgement.
informationalmildnephrotic_or_malabsorption_rising_requirement
Unexplained TSH rise on a previously stable, correctly-taken levothyroxine dose with nephrotic-range proteinuria, CKD, celiac/IBD, or post-bariatric malabsorption — increased requirement, not non-adherence (J Clin Diagn Res 2016; Eur Thyroid J 2015)
Trigger could not be auto-evaluated — needs clinician judgement.

Workflow calculators

Run this disease's risk and dosing calculators inline.

INITIAL_WORKUPrequiredDrives screening

Loading…

Recommended regimen

Hypothyroidism levothyroxine ladder — exclude central / treat reversible → overt full replacement → subclinical threshold → titration & absorption → persistent-symptom T3 (experimental) → pregnancy → geriatric/CAD start-low (ATA 2014 Jonklaas; ATA 2017 Alexander; ETA 2013 Pearce)

axis: hypothyroidism_levothyroxine_phenotype_ladderstep 1 - Step 1 — Phenotype gate: exclude central / NTIS / transient; treat reversible cause (no chronic LT4 yet)

Selected step "Step 1 — Phenotype gate: exclude central / NTIS / transient; treat reversible cause (no chronic LT4 yet)" — Any abnormal TSH/FT4 before committing to lifelong replacement

glucocorticoid BEFORE levothyroxine if central + possible adrenal insufficiency
first line
sequencing_safety_rule
triggers: suspected_central_hypothyroidism, possible_adrenal_insufficiency
ATA 2014 — in central disease give hydrocortisone first; levothyroxine before cortisol can precipitate adrenal crisis; route to endo.hypopituitarism.core.v1
defer treatment and retest after recovery (non-thyroidal illness)
first line
treatment_deferral
triggers: acute_severe_illness_ntis_pattern
ATA 2014 — NTIS (low T3/FT4 + low/normal TSH in acute illness) is not primary hypothyroidism; do not treat, retest after recovery
remove / reassess thyroid-toxic drug and retest (transient vs permanent — quantified by agent)
comorbidity specific
medication_reconciliation
triggers: amiodarone, lithium, immune_checkpoint_inhibitor, pd1_pdl1_inhibitor, ctla4_inhibitor, tyrosine_kinase_inhibitor, interferon, postpartum_2_to_12_months
ATA 2014 — drug-induced / post-partum thyroiditis may be transient; characterise before lifelong therapy. Agent-specific pre-test: lithium clinical hypothyroidism OR 5.78 (95% CI 2.00–16.67) vs placebo, mean TSH +4.00 mIU/mL (McKnight Lancet 2012, PMID 22265699) — usually requires LT4 not drug-stop; immune-checkpoint inhibitors PD-1/PD-L1 hypothyroidism ~8% incidence and OR 1.89 (1.17–3.05) vs ipilimumab, combination OR 3.81 (2.10–6.91) — often after a thyrotoxic phase, then permanent → replace, do NOT stop oncologic therapy (Barroso-Sousa JAMA Oncol 2018 PMID 28973656; de Filette Horm Metab Res 2019 PMID 30861560); amiodarone-induced hypothyroidism is more common in iodine-replete/TPO-Ab+ patients and usually does NOT require amiodarone withdrawal (ATA 2014 25266247); postpartum thyroiditis hypothyroid phase (2–12 mo) is frequently transient — retest off insult before lifelong commitment

outpatient playbook — drug actions (7)

1. phenotype gate — glucocorticoid-first if central; defer if NTIS; reassess drug/post-partum if transient
no chronic LT4 yet • n/a • once
trigger: Any abnormal TSH/FT4
Exclude central/NTIS/transient and treat reversible cause before lifelong therapy (ATA 2014 Jonklaas)
2. levothyroxine — overt primary full replacement
1.6 µg/kg/day single AM dose • PO • once daily
trigger: TSH high + FT4 low, no cardiac caution, not pregnant
ATA 2014 Jonklaas (PMID 25266247) — weight-based full replacement, LT4 monotherapy
3. levothyroxine — subclinical by threshold
25–75 µg/day if TSH >10; 25–50 µg trial if 4.5–10 + symptoms (stop at 3–4 mo if no benefit) • PO • once daily
trigger: TSH high + FT4 normal
ETA 2013 Pearce (24783053); Floriani/Rodondi CHD HR 1.58 ≥10 (28329380); Feller null SMD −0.11 (30285179)
4. levothyroxine — titrate + manage absorption
adjust 12.5–25 µg; recheck TSH q6–8 wk; separate from PPI/Ca/Fe/fiber 4 h • PO • once daily
trigger: TSH off target / interaction present
ATA 2014 Jonklaas (25266247)
5. liothyronine added to levothyroxine — EXPERIMENTAL specialist-only
LT4/LT3 ratio 13:1–20:1, LT3 BID; stop at 3 mo if no benefit • PO • LT4 daily + LT3 BID
trigger: Persistent symptoms, euthyroid, autoimmune disease excluded, specialist-supervised
2012 ETA Wiersinga (24782999) + 2021 ATA/BTA/ETA consensus (33276704)
6. levothyroxine — pregnancy dose escalation
+20–30% at confirmation; titrate to trimester-specific TSH • PO • once daily
trigger: Pregnancy confirmed / pre-conception
ATA 2017 Alexander (28056690); treated SCH pregnancy-loss OR 0.55 (34956101)
7. levothyroxine — geriatric/CAD low-and-slow
25–50 µg/day, +12.5–25 µg q4–6 wk by TSH + cardiac tolerance • PO • once daily
trigger: Age >65–70 and/or CAD/IHD/arrhythmia
ATA 2014 Jonklaas (25266247) — avoid precipitating ischaemia/AF

Auto-drafted A&P note

outpatient

Subjective

- Possible entry pathways: Elevated TSH on screening / opportunistic testing (ATA 2014 Jonklaas; ETA 2013 Pearce); Low free T4 with low / inappropriately-normal TSH — central pattern (ATA 2014; central CH not always mild, JCEM 2014); Fatigue / cold intolerance / weight gain / constipation / dry skin (low-specificity cluster) (ATA 2014 Jonklaas).

Objective

- No vitals, labs, or imaging entered for this encounter.

Assessment

**Hypothyroidism (overt / subclinical / central — standalone core)** (endo.hypothyroidism.core.v1).
Phenotype framing: MECE terminal split: overt primary hypothyroidism (Hashimoto / iatrogenic / iodine / congenital) vs subclinical primary vs central (secondary/tertiary) hypothyroidism vs non-thyroidal illness syndrome vs transient thyroiditis / drug-induced dysfunction. The TSH/FT4 pattern conditional on pregnancy / illness / pituitary status is decisive (ATA 2014 Jonklaas)
Scope: Hypothyroidism is a biochemical state requiring a mandatory phenotype split BEFORE levothyroxine: overt primary vs subclinical vs central vs non-thyroidal illness vs transient (thyroiditis/drug). Treatment target, treat-threshold, and safety steps differ by phenotype (ATA 2014 Jonklaas)

No severity triggers fired against current inputs.

Plan

Regimen axis: **Hypothyroidism levothyroxine ladder — exclude central / treat reversible → overt full replacement → subclinical threshold → titration & absorption → persistent-symptom T3 (experimental) → pregnancy → geriatric/CAD start-low (ATA 2014 Jonklaas; ATA 2017 Alexander; ETA 2013 Pearce)** — step "Step 1 — Phenotype gate: exclude central / NTIS / transient; treat reversible cause (no chronic LT4 yet)".
1. glucocorticoid BEFORE levothyroxine if central + possible adrenal insufficiency (sequencing_safety_rule, first line) — ATA 2014 — in central disease give hydrocortisone first; levothyroxine before cortisol can precipitate adrenal crisis; route to endo.hypopituitarism.core.v1
2. defer treatment and retest after recovery (non-thyroidal illness) (treatment_deferral, first line) — ATA 2014 — NTIS (low T3/FT4 + low/normal TSH in acute illness) is not primary hypothyroidism; do not treat, retest after recovery
3. remove / reassess thyroid-toxic drug and retest (transient vs permanent — quantified by agent) (medication_reconciliation, comorbidity specific) — ATA 2014 — drug-induced / post-partum thyroiditis may be transient; characterise before lifelong therapy. Agent-specific pre-test: lithium clinical hypothyroidism OR 5.78 (95% CI 2.00–16.67) vs placebo, mean TSH +4.00 mIU/mL (McKnight Lancet 2012, PMID 22265699) — usually requires LT4 not drug-stop; immune-checkpoint inhibitors PD-1/PD-L1 hypothyroidism ~8% incidence and OR 1.89 (1.17–3.05) vs ipilimumab, combination OR 3.81 (2.10–6.91) — often after a thyrotoxic phase, then permanent → replace, do NOT stop oncologic therapy (Barroso-Sousa JAMA Oncol 2018 PMID 28973656; de Filette Horm Metab Res 2019 PMID 30861560); amiodarone-induced hypothyroidism is more common in iodine-replete/TPO-Ab+ patients and usually does NOT require amiodarone withdrawal (ATA 2014 25266247); postpartum thyroiditis hypothyroid phase (2–12 mo) is frequently transient — retest off insult before lifelong commitment

Setting playbook (outpatient) — Phenotype-split the hypothyroidism, treat the right phenotype with the right target, titrate levothyroxine to a phenotype-appropriate goal, manage pregnancy/elderly/CAD/central special cases, and avoid over-replacement (ATA 2014 Jonklaas; ATA 2017 Alexander; ETA 2013 Pearce)
4. phenotype gate — glucocorticoid-first if central; defer if NTIS; reassess drug/post-partum if transient no chronic LT4 yet n/a once — Any abnormal TSH/FT4 (Exclude central/NTIS/transient and treat reversible cause before lifelong therapy (ATA 2014 Jonklaas))
5. levothyroxine — overt primary full replacement 1.6 µg/kg/day single AM dose PO once daily — TSH high + FT4 low, no cardiac caution, not pregnant (ATA 2014 Jonklaas (PMID 25266247) — weight-based full replacement, LT4 monotherapy)
6. levothyroxine — subclinical by threshold 25–75 µg/day if TSH >10; 25–50 µg trial if 4.5–10 + symptoms (stop at 3–4 mo if no benefit) PO once daily — TSH high + FT4 normal (ETA 2013 Pearce (24783053); Floriani/Rodondi CHD HR 1.58 ≥10 (28329380); Feller null SMD −0.11 (30285179))
7. levothyroxine — titrate + manage absorption adjust 12.5–25 µg; recheck TSH q6–8 wk; separate from PPI/Ca/Fe/fiber 4 h PO once daily — TSH off target / interaction present (ATA 2014 Jonklaas (25266247))
8. liothyronine added to levothyroxine — EXPERIMENTAL specialist-only LT4/LT3 ratio 13:1–20:1, LT3 BID; stop at 3 mo if no benefit PO LT4 daily + LT3 BID — Persistent symptoms, euthyroid, autoimmune disease excluded, specialist-supervised (2012 ETA Wiersinga (24782999) + 2021 ATA/BTA/ETA consensus (33276704))
9. levothyroxine — pregnancy dose escalation +20–30% at confirmation; titrate to trimester-specific TSH PO once daily — Pregnancy confirmed / pre-conception (ATA 2017 Alexander (28056690); treated SCH pregnancy-loss OR 0.55 (34956101))
10. levothyroxine — geriatric/CAD low-and-slow 25–50 µg/day, +12.5–25 µg q4–6 wk by TSH + cardiac tolerance PO once daily — Age >65–70 and/or CAD/IHD/arrhythmia (ATA 2014 Jonklaas (25266247) — avoid precipitating ischaemia/AF)

Non-pharmacologic actions:
- Consistent timing + fasting administration counselling; separate interacting agents by 4 h (ATA 2014 Jonklaas)
- Route central hypothyroidism to endo.hypopituitarism.core.v1 (full axis + adrenal-first) (ATA 2014 Jonklaas)
- Pre-conception planning for women of reproductive age — optimise before pregnancy, plan the ~20–30% bump (ATA 2017 Alexander)
- Re-test (do not treat) non-thyroidal illness after recovery (ATA 2014 Jonklaas)
- Characterise transient (post-partum / drug) thyroiditis before committing to lifelong therapy (ATA 2014 Jonklaas)

AVOID / contraindication checks:
- Central_hypothyroidism_do_not_titrate_to_TSH_use_mid_normal_FT4 (ATA 2014 Jonklaas 25266247)
- Give_glucocorticoid_before_levothyroxine_if_central_with_possible_adrenal_insufficiency (ATA 2014 Jonklaas 25266247)
- Elderly_and_CAD_start_25_50_mcg_and_uptitrate_slowly_to_avoid_ischaemia_or_AF (ATA 2014 Jonklaas 25266247)
- Avoid_over_replacement_suppressed_TSH_increases_AF (HR 1.45 high normal FT4, Circulation 29061566) and fracture (subclinical hyper hip fracture HR 1.36, JAMA 26010634)
- Do_not_treat_non_thyroidal_illness_syndrome_retest_after_recovery (ATA 2014 Jonklaas 25266247)
- Combination_LT4_LT3_experimental_specialist_only_ratio_13to1_to_20to1_stop_at_3_months_if_no_benefit (2012 ETA 24782999; 2021 ATA/BTA/ETA 33276704)
- Separate_levothyroxine_from_PPI_calcium_iron_fiber_by_4h_account_for_estrogen_and_malabsorption (ATA 2014 Jonklaas 25266247)
- Unexplained_TSH_rise_on_stable_dose_work_up_nephrotic_proteinuria_and_malabsorption_before_assuming_non_adherence_LT4_need_rises_~18pct (PMID 28208903; 26280000)
- Checkpoint_inhibitor_or_lithium_or_amiodarone_induced_hypothyroidism_usually_replace_do_not_stop_the_culprit_drug (lithium OR 5.78 McKnight 22265699; ICI OR 1.89–3.81 28973656/30861560; ATA 2014 25266247)
- Myxedema_decompensation_escalate_to_endo.myxedema coma.core.v1 (acute engine; not managed here)

Monitoring

Regimen monitoring:
- TSH ~6–8 weeks after each dose change then every 6–12 months once stable (primary disease) (ATA 2014 Jonklaas 25266247)
- free T4 mid-normal target — NOT TSH — in central hypothyroidism (ATA 2014 Jonklaas 25266247)
- TSH ~every 4 weeks in first half of pregnancy then at least once mid-2nd/3rd trimester (ATA 2017 Alexander 28056690)
- screen for over-replacement (suppressed TSH) — AF and fracture risk (Circulation 29061566; JAMA 26010634)
- subclinical symptom trial: reassess at 3–4 months with in-range TSH and STOP if no benefit (ETA 2013 Pearce 24783053)
- combination LT4/LT3 trial: discontinue at 3 months if no improvement (2012 ETA 24782999; 2021 consensus 33276704)
- nephrotic/CKD/malabsorption: recheck TSH 6–8 weeks after a ~15–20% dose change; track CKD-EPI-2021 eGFR + urine protein:creatinine and step LT4 back down on nephrotic remission (PMID 28208903; 26280000)
- lithium / amiodarone / immune-checkpoint-inhibitor on therapy: baseline + periodic TSH surveillance (lithium hypothyroidism OR 5.78, McKnight 22265699; ICI hypothyroidism ~8% PD-1, OR 1.89–3.81, 28973656/30861560)

Setting (outpatient) monitoring:
- TSH ~6–8 weeks after dose change then 6–12 monthly (primary) (ATA 2014 Jonklaas)
- Free T4 (mid-normal) not TSH in central disease (ATA 2014 Jonklaas)
- TSH ~q4 weeks first-half pregnancy then mid-2nd/3rd trimester (ATA 2017 Alexander)
- Screen for over-replacement (suppressed TSH → AF/fracture) at each visit (Circulation 29061566; JAMA 26010634)

Follow-up plan: Lifelong replacement for permanent primary and central disease (transient may be weaned and retested). Reinforce adherence + consistent timing + absorption-interaction counselling; pre-conception planning for women of reproductive age (optimise pre-pregnancy, plan the ~20–30% bump); annual TSH once stable; reassess persistent-symptom patients (chronic-disease support, exclude associated autoimmune disease) before any combination trial (ATA 2014 Jonklaas; ATA 2017 Alexander; 2021 ATA/BTA/ETA combination consensus)
- Close-out criterion: Lifelong / wean plan, adherence counselling and pre-conception plan booked

Monitoring phase: Primary: recheck TSH ~6–8 weeks after every dose change until stable, then every 6–12 months. Central: monitor FT4 (mid-normal target) — TSH is uninformative. Pregnancy: TSH approximately every 4 weeks in the first half then at least once mid-second/third trimester. Watch for over-replacement (suppressed TSH → AF risk HR 1.45 high-normal FT4; subclinical-hyperthyroid hip-fracture HR 1.36) (ATA 2014 Jonklaas; ATA 2017 Alexander; ETA 2013 Pearce)

Disposition

Current setting: outpatient — Phenotype-split the hypothyroidism, treat the right phenotype with the right target, titrate levothyroxine to a phenotype-appropriate goal, manage pregnancy/elderly/CAD/central special cases, and avoid over-replacement (ATA 2014 Jonklaas; ATA 2017 Alexander; ETA 2013 Pearce)

Disposition criteria:
- Continue outpatient endocrinology / primary care once stable on a phenotype-appropriate dose (ATA 2014 Jonklaas)
- Transfer/route central disease to hypopituitarism engine; escalate myxedema decompensation to the acute engine (ATA 2014 Jonklaas)

Escalation triggers (move to higher acuity):
- Myxedema decompensation (hypothermia, depressed consciousness, hypoventilation, bradycardia) → ED, escalate to endo.myxedema-coma.core.v1 (ATA 2014 Jonklaas)
- Suspected central hypothyroidism with possible adrenal crisis → urgent endocrinology + glucocorticoid before levothyroxine; route to endo.hypopituitarism.core.v1 (ATA 2014 Jonklaas)
- New angina / arrhythmia on levothyroxine initiation in CAD → reduce dose + cardiology (ATA 2014 Jonklaas)
- Pregnancy with rising TSH above trimester target → expedite dose increase + obstetric co-management (ATA 2017 Alexander)

Patient Action Plan

**Hypothyroidism levothyroxine self-management plan**
Personalised values: levothyroxine_dose, phenotype, tsh_target, pregnancy_plan, cardiac_status.

**Stable, TSH at target** (green):
Triggers:
- TSH within your individual target range (ATA 2014 Jonklaas)
- No new symptoms; stable dose ≥6 months
- Taking levothyroxine consistently on an empty stomach
Actions:
- Take levothyroxine every day at the same time on an empty stomach (ATA 2014 Jonklaas)
- Separate it from antacids/PPI, calcium, iron and fiber by about 4 hours (ATA 2014 Jonklaas)
- Keep your TSH check every 6–12 months (ATA 2014 Jonklaas)
- Tell any prescriber you take thyroid hormone before starting estrogen or new medicines (ATA 2014 Jonklaas)
- If you plan a pregnancy, contact your provider FIRST to optimise the dose (ATA 2017 Alexander)

**Symptoms changing, dose recently changed, or newly pregnant** (yellow):
Triggers:
- Return of fatigue / cold intolerance / weight change
- Palpitations, tremor or trouble sleeping (possible over-replacement)
- A positive pregnancy test while on levothyroxine
- New medicine that affects absorption started
Actions:
- If you are newly pregnant, contact your provider NOW — your dose usually needs to go up about 20–30% immediately (ATA 2017 Alexander)
- Do not change your own dose; arrange a TSH check (ATA 2014 Jonklaas)
- Report palpitations/tremor — these can mean too much thyroid hormone (Circulation 29061566)
- Bring an updated medication list to your visit (ATA 2014 Jonklaas)
Contact provider when:
- Newly pregnant on levothyroxine (same day) (ATA 2017 Alexander)
- New or worsening palpitations / chest symptoms (ATA 2014 Jonklaas)
- Symptoms persist despite a normal TSH (ATA 2014 Jonklaas)

**Severe decompensation** (red):
Triggers:
- Profound lethargy / confusion / unresponsiveness
- Feeling very cold with slow breathing or very slow heart rate
- Severe weakness after stopping levothyroxine for a long period
Actions:
- Call emergency services or go to the emergency department now
- This can be myxedema coma — a medical emergency (ATA 2014 Jonklaas)
- Bring your medication list including your levothyroxine dose
Contact provider when:
- Always seek emergency care for confusion + hypothermia + slow breathing (myxedema decompensation) (ATA 2014 Jonklaas)

Earlier-Return Triggers

Return-precaution thresholds (watch for):
- [LIFE_THREATENING] Hypothermia + depressed consciousness + hypoventilation/bradycardia ± hyponatremia in a hypothyroid patient — myxedema coma (ATA 2014 Jonklaas)
- [SEVERE] Low/inappropriately-normal TSH + low FT4 suggesting central disease, especially with sellar mass / cranial RT / Sheehan / TBI and possible adrenal insufficiency (ATA 2014 Jonklaas; JCEM 2014 — central CH not always mild)
- [SEVERE] Hypothyroid (overt or subclinical, esp. TPO-Ab+) woman who is pregnant or planning pregnancy (ATA 2017 Alexander)

Citations

- ATA 2014 Guidelines for the Treatment of Hypothyroidism (Jonklaas, Thyroid 2014) + ATA 2017 Thyroid Disease in Pregnancy (Alexander) + 2013 ETA Subclinical Hypothyroidism (Pearce) + 2012 ETA / 2021 ATA-BTA-ETA LT4-LT3 combination consensus; reconciled with TRUST (Stott NEJM 2017) and Thyroid Studies Collaboration IPD meta-analyses [PMID:25266247](https://pubmed.ncbi.nlm.nih.gov/25266247/)
- Cited evidence (PMID 28056690) [PMID:28056690](https://pubmed.ncbi.nlm.nih.gov/28056690/)
- Cited evidence (PMID 28402245) [PMID:28402245](https://pubmed.ncbi.nlm.nih.gov/28402245/)
- Cited evidence (PMID 30285179) [PMID:30285179](https://pubmed.ncbi.nlm.nih.gov/30285179/)
- Cited evidence (PMID 28329380) [PMID:28329380](https://pubmed.ncbi.nlm.nih.gov/28329380/)

Last reconciled with current guidelines: 2026-05-17.

References

ATA 2014 Guidelines for the Treatment of Hypothyroidism (Jonklaas, Thyroid 2014) + ATA 2017 Thyroid Disease in Pregnancy (Alexander) + 2013 ETA Subclinical Hypothyroidism (Pearce) + 2012 ETA / 2021 ATA-BTA-ETA LT4-LT3 combination consensus; reconciled with TRUST (Stott NEJM 2017) and Thyroid Studies Collaboration IPD meta-analyses — PMID:25266247
Cited evidence (PMID 28056690) — PMID:28056690
Cited evidence (PMID 28402245) — PMID:28402245
Cited evidence (PMID 30285179) — PMID:30285179
Cited evidence (PMID 28329380) — PMID:28329380