TCS Industries Limited (China-sourced API supplier) supplies Levothyroxine Sodium — API CAS 55-03-8 for pharmaceutical B2B procurement — COA, MSDS, and technical documentation available on request.
> Overview
| Product Name | Levothyroxine Sodium |
|---|---|
| Structural Formula |  |
| CAS Number | 55-03-8 |
| Molecular Formula | C15H10I4NNaO4 |
| Molecular Weight | 798.85 g/mol |
| InChIKey | YDTFRJLNMPSCFM-YDALLXLXSA-M |
| SMILES | Available on request where applicable |
| Appearance | White to off-white hygroscopic powder |
| Purity / Grade | By agreed specification and batch COA |
| Storage | Store at controlled room temperature, protect from light and moisture |
Levothyroxine Sodium (CAS 55-03-8) is the sodium salt of L-thyroxine (T4), the primary thyroid hormone. It has the formula C₁₅H₁₀I₄NNaO₄ (MW 798.85). Levothyroxine is the standard treatment for hypothyroidism and thyroid cancer suppression therapy. It is a widely prescribed medication globally and is on the WHO Model List of Essential Medicines.
TCS Industries Limited, a Hong Kong-based trading and sourcing company, supplies Levothyroxine Sodium API in pharmaceutical grade for global procurement programs.
> Applications
Hypothyroidism treatment
Levothyroxine sodium at 1.6 μg/kg/day is the standard replacement therapy for primary hypothyroidism. It is converted to the active T3 form by tissue deiodinases. Dose is titrated to normalize TSH (0.4–4.0 mIU/L). Jonklaas et al. (Thyroid, 2014, 24:1670–1751) published the ATA/AACE guidelines establishing levothyroxine monotherapy as the standard of care for hypothyroidism with detailed recommendations on dosing, monitoring, and special populations.
Thyroid cancer suppression
Levothyroxine is used at supra-physiological doses (target TSH 0.1–0.5 or <0.1 mIU/L depending on risk) to suppress TSH-dependent thyroid cancer growth after thyroidectomy. This requires higher doses than simple replacement. Dose adjustment considers both thyroid cancer recurrence risk and cardiovascular/bone health risks of TSH suppression.
> Sourcing & Supply
TCS Industries Limited supports development, qualification and commercial purchasing discussions for Levothyroxine Sodium with buyers in Australia, New Zealand, Canada and South Korea.
- Evaluation and commercial quantities: 10 g samples for analytical qualification; 100 g and 1 kg for production. Pharmaceutical (USP/Ph.Eur.) grade. NTI drug with strict potency requirements. DMF reference letters available.
- Pallet quantities and production campaigns: repeat supply is coordinated against packaging, lead time, annual demand and destination-market import requirements.
> Quality & Documentation
Key specification parameters include assay (≥98.0%), related substances (liothyronine, diiodothyronine), specific optical rotation, loss on drying, sodium content, heavy metals, and microbial limits. White to slightly colored powder. Slightly soluble in water, soluble in dilute alkali. Four iodine atoms per molecule (~65% iodine by weight). Identity by HPLC and IR. Meets USP (Levothyroxine Sodium), Ph.Eur. (Levothyroxinum natricum), and BP. NTI drug — tight potency specifications. COA and MSDS are standard.
> Packaging
Levothyroxine sodium is a white to slightly colored powder, sensitive to light, heat, and humidity. High-potency API — microgram dosing. Standard packaging includes amber glass bottles or sealed foil bags under nitrogen (10 g, 50 g, 100 g, or 1 kg). Store at controlled room temperature (15–25 °C). Protect from light and moisture. Shelf life is typically 24 months. Labels and documents are checked before dispatch.
> Pricing & MOQ
Pricing is quoted by specification, packaging and destination. Common commercial discussions use 25 kg bag/drum formats, pallet quantities and production-campaign planning; smaller samples may be reviewed for qualified formulation teams.
> Regulatory & Compounding Context
Levothyroxine sodium is monographed in USP, Ph.Eur. (Levothyroxinum natricum), BP, and JP. FDA-approved (Synthroid, 2002 NDA after years of marketed-without-approval status). On the WHO Model List of Essential Medicines. Classified as NTI (narrow therapeutic index) drug in the US, requiring ±5% potency through shelf life. Multiple generic approvals with AB-rating bioequivalence. DMF support available.
> Alias Index
- INN: Levothyroxine
- CAS Number: 55-03-8 (sodium salt); 51-48-9 (free acid, L-T4)
- Formula: C₁₅H₁₀I₄NNaO₄ (MW 798.85)
- Abbreviation: T4 (thyroxine)
- Brand names: Synthroid, Levoxyl, Euthyrox, Tirosint
- ATC code: H03AA01
- Commercial request terms: levothyroxine sodium API, T4 hormone bulk, Synthroid generic, thyroid API, TCS Industries Limited
> FAQ
Why is Levothyroxine classified as NTI?
Small dose changes (±12.5 μg) produce clinically significant TSH shifts. FDA requires potency between 95–105% of label claim throughout shelf life (vs. 90–110% for most drugs). Generic substitution requires AB-rated bioequivalence with tighter confidence intervals. This strict specification drives API quality requirements for assay and stability.
What documents are available for Levothyroxine Sodium orders?
COA and MSDS are standard for commercial discussions. COO, packing list, invoice and other import-support documents can be arranged according to order scope.
Do you supply Levothyroxine Sodium to Australia and Canada?
Yes. We support B2B buyers in Australia, New Zealand, Canada and South Korea, subject to route and document review.
Do you supply New Zealand and South Korea?
Yes. We review Australia, New Zealand, Canada and South Korea for project supply, import documents, packaging and logistics planning before quotation.
Why is T4 preferred over T3 for replacement?
T4 (levothyroxine) has a 7-day half-life, providing stable serum levels with once-daily dosing. The body converts T4 to T3 via deiodinases as needed, mimicking physiological regulation. T3 (liothyronine) has a 1-day half-life, causing serum level fluctuations. T4 monotherapy normalizes both T4 and T3 levels in most patients.
Is stability a concern for Levothyroxine?
Yes. Levothyroxine is susceptible to degradation by light, heat, and moisture. Finished products historically had stability problems (leading to FDA requiring new NDAs for all marketed products in 2001). API must be stored protected from light in desiccated, controlled-temperature conditions. Excipient compatibility studies are critical in formulation.
Can you arrange samples before commercial purchasing?
Samples or evaluation quantities may be reviewed for qualified buyers after target specification, application and destination-market requirements are clarified.
How is Levothyroxine Sodium packaged for export?
Packaging is confirmed by quantity and material properties. Typical options include foil bags, HDPE containers, fibre drums, 25 kg bags or palletized export packaging.
Can buyer-defined specifications be reviewed?
Yes. Send the specification, methods, impurity limits and required documents. TCS can review feasibility before confirming quotation and lead time.
What payment terms are normally used?
Standard payment is 100% T/T before dispatch unless a different arrangement has been approved for an established commercial account.
What lead time should buyers expect?
Lead time depends on stock, batch size, document scope and destination. Available stock can move faster; made-to-order or pallet programs require longer planning.
What formulation types are available?
Oral tablets (25–300 μg), soft gelatin capsules (Tirosint), and oral solution. Tablets are the standard dosage form, using direct compression with minimal excipients. IV injection is available for myxedema coma. Soft gelatin capsules (liquid T4 in gelatin shell) avoid excipient interactions and moisture sensitivity issues seen with tablets.
Last reviewed: June 2026
Evaluation and research orders (≤10 kg) are shipped with COA, MSDS, and certificate of origin. Bulk commercial orders (>10 kg) qualify for volume pricing with a full technical documentation package available on request.
> Request a Quote
If your team already has a target application, estimated quantity, destination market, or documentation requirements, send those details so the commercial response can be prepared more efficiently.