Summary

ATA 2014 task force guideline on treatment of hypothyroidism, addressing 24 clinical questions across levothyroxine therapy, alternative preparations (combination LT4/LT3, desiccated thyroid, LT3 monotherapy, compounded products, nutraceuticals), special populations (elderly, pregnant, pediatric, hospitalized), myxedema coma, and thyroid hormone analogs. Reaffirms levothyroxine monotherapy as standard of care, finding no consistent evidence that LT4/LT3 combination therapy, thyroid extracts, or analogs are superior. Provides specific guidance on dosing, drug/food interactions, TSH targets, and management of nonadherence and nonthyroidal illness.

Key Recommendations

Levothyroxine monotherapy is the standard of care for hypothyroidism; combination LT4/LT3, desiccated thyroid extract, and compounded preparations are not recommended for routine use.
Target serum TSH within the reference range (0.4–4.0 mIU/L) for primary hypothyroidism; do not adjust dose based on symptoms alone when TSH is normal.
Take levothyroxine consistently 60 minutes before breakfast or at bedtime (≥3 hours after evening meal); separate from calcium, iron, PPIs, bile acid sequestrants, and phosphate binders.
Maintain patients on the same identifiable LT4 formulation (brand or generic); recheck TSH 4–6 weeks after any product switch.
Initiate LT4 at full replacement dose (~1.6 μg/kg/d) in young healthy adults; start low (12.5–25 μg/d) and titrate slowly in elderly and those with known CAD.
In pregnancy, increase LT4 dose by ~2 extra tablets/week as soon as pregnancy confirmed; target trimester-specific TSH (1st: 0.1–2.5; 2nd: 0.2–3.0; 3rd: 0.3–3.0 mIU/L); monitor TSH every 4 weeks in first half of pregnancy.
Treat congenital hypothyroidism with LT4 10–15 μg/kg/d immediately upon positive newborn screen; aim to normalize T4 within 2–4 weeks; target TSH 0.5–2.0 mIU/L.
In the elderly (>70–80 years), accept higher TSH targets (up to 4–6 mIU/L) and avoid overtreatment due to risks of atrial fibrillation and fractures, particularly with TSH <0.1 mIU/L.
For secondary (central) hypothyroidism, titrate LT4 to maintain free T4 in the upper half of the reference range; do not use TSH as the therapeutic target.
Evaluate for H. pylori gastritis, atrophic gastritis, or celiac disease when LT4 requirements are unexpectedly high; reassess dose after treatment of these conditions.
Treat myxedema coma with IV LT4 loading dose 200–400 μg followed by 1.6 μg/kg/d (75% of oral dose IV); add IV LT3 (5–20 μg load, then 2.5–10 μg q8h); give empiric stress-dose glucocorticoids before thyroid hormone.
Do not treat nonthyroidal illness syndrome with LT4 or LT3; do not use LT4 to treat obesity, depression, urticaria, or nonspecific symptoms in euthyroid patients.
For suspected nonadherence with elevated TSH despite high doses, consider weekly oral LT4 (7× daily dose) under supervision after confirming absorption.
There is no credible evidence supporting ‘Wilson’s temperature syndrome’; T3 escalation therapy for this entity is not recommended due to risk of iatrogenic thyrotoxicosis.

Thresholds & Doses

Standard LT4 replacement: ~1.6 μg/kg/d actual body weight (1.6–1.8 μg/kg/d in athyreotic adults).
TSH-suppressive thyroid cancer doses: 2.1–2.7 μg/kg/d.
Pediatric LT4 dosing: newborns 10–15 μg/kg/d; age 1–3 yr 4–6 μg/kg/d; age 3–10 yr 3–5 μg/kg/d; age 10–16 yr 2–4 μg/kg/d.
Adult TSH target: 0.4–4.0 mIU/L (reference range); elderly >70–80 yr: 4–6 mIU/L acceptable.
Pregnancy trimester-specific TSH targets: 1st trimester 0.1–2.5 mIU/L; 2nd trimester 0.2–3.0 mIU/L; 3rd trimester 0.3–3.0 mIU/L; preconception <2.5 mIU/L.
Pregnancy LT4 adjustment: add 2 extra doses/week as soon as pregnancy confirmed; monitor TSH every 4–6 weeks in first half of pregnancy.
Steady-state TSH reached ~6 weeks after dose change; recheck TSH 4–6 weeks after any adjustment, then every 4–6 months, then annually.
LT4 dose titration increments: 12.5–25 μg/d.
Initial LT4 in CAD/elderly: 12.5–25 μg/d with gradual titration.
IV LT4 equivalent dose: ~75% of oral dose.
Myxedema coma LT4 loading: 200–400 μg IV; maintenance 1.6 μg/kg/d (×0.75 if IV).
Myxedema coma LT3: load 5–20 μg IV, then 2.5–10 μg q8h.
Avoid TSH <0.1 mIU/L in elderly/postmenopausal women due to 3× risk of atrial fibrillation and increased fracture risk.
Pediatric subclinical hypothyroidism: treatment generally not recommended for TSH 5–10 mIU/L; consider treatment if TSH >10 mIU/L with symptoms or risk factors.
Cardiovascular risk increases with TSH >10 mIU/L (and possibly >7 mIU/L).
FDA potency requirement for LT4: 95%–105% throughout shelf life.
LT4 oral bioavailability: 70%–80% under fasting conditions.
LT4 serum half-life: ~7 days; LT3 half-life: ~1 day.
Pediatric congenital hypothyroidism monitoring: TSH/T4 every 1–2 months in first year of life.

Citations

Recommendation 1a — Levothyroxine as standard of care for hypothyroidism (Strong, Moderate evidence).
Recommendation 1b — TSH normalization as goal of therapy; avoid overtreatment (Strong, Moderate evidence).
Recommendations 3a–3b — Timing of LT4 administration and drug interactions (calcium, iron, PPIs, bile acid sequestrants).
Recommendation 4a–4b — Weight-based LT4 dosing (1.6 μg/kg/d) and titration approach.
Recommendation 6a — Higher TSH targets in elderly (>65–70 years).
Recommendation 6b — Trimester-specific TSH targets and dose increase in pregnancy.
Recommendation 6c — Pediatric and congenital hypothyroidism dosing (10–15 μg/kg/d).
Recommendations 13b–13c — Against routine LT4/LT3 combination therapy (Weak, Moderate evidence).
Recommendations 21a–21d — Myxedema coma management with IV LT4 loading, LT3, and empiric glucocorticoids.
Recommendation 22a–22b — Against thyroid hormone replacement in nonthyroidal illness syndrome.
Recommendation 19 — Against ‘Wilson’s syndrome’ T3 escalation therapy.
Table 5 — Medications reducing LT4 absorption (calcium, iron, PPIs, sucralfate, bile acid sequestrants).