Levothyroxine Suppressive Therapy in Thyroid Cancer

R Michael Tuttle, MD

Attending EndocrinologistAssistant Professor of Medicine

Memorial Sloan Kettering Cancer CenterSanford Weill Medical College of Cornell University

New York, NY

Estimated New CasesUnited States, 2003

Breast

Prostate

Lung

Colon

Lymphoma

Leukemia

Kidney

Thyroid

Multiple Myeloma

Hodgkin

50 k 100k 150k 200k 250k

22,000 new cases1,400 deaths

American Cancer Society

Standard Initial Treatment Usual Pathway

TotalThyroidectomy

Remove the thyroid with all cancerous tissue

Radioactive IodineTreatment

Destroy any microscopic residual

thyroid tissue

Completely dependent on exogenous levothyroxine

Without any functional thyroid

tissue

Levothyroxine Therapy Thyroid Cancer

NormalizeTSH

Prevent Symptoms of Hypothyroidism

SuppressTSH

Decreased Risk of Recurrence of Thyroid

Cancer

Without any functional thyroid

tissue

Levothyroxine Suppression

Free T4 Normal Range

(ng/dL)

TSH Normal Range

(mcU/mL)

0.8

2.0

0.4

4.4

<0.010.1

PrimaryHypothyroidism

ThyroidCancer

HyperthyroidSymptoms

IncreasedRecurrence

TSH Suppression

Levothyroxine Suppression

Free T4 Normal Range

(ng/dL)

TSH Normal Range

(mcU/mL)

0.8

2.0

0.4

4.4

<0.010.1TSH

Suppression

12-15%increase

12-15%decrease

ThyroidCancer

HyperthyroidSymptoms

IncreasedRecurrence

ThyroidCancer

Levothyroxine Suppression Therapy

• Thyroid cancer

• Very narrow therapeutic window• Small changes in administered dose

•Symptomatic hyperthyroidism•Recurrence of disease

• Product substitution with alternatives that vary

by more than 5-10% from the brand name

product would be unacceptable in the

treatment of thyroid cancer.

Treatment GuidelinesThyroid Cancer

Singer PA, Cooper DS, Daniels GH et al. Treatment guidelines for patients with thyroid nodules and well-differentiated thyroid cancer. American Thyroid Association. Arch Intern Med. 1996 Oct 28;156(19):2165-72.

AACE/AAES medical/surgical guidelines for clinical practice: management of thyroid carcinoma. American Association of Clinical Endocrinologists. American College of Endocrinology. Endocr Pract. 2001 May-Jun;7(3):202-20.

British Thyroid Association. Guidelines for the management of thyroid cancer. London: Royal College of Physician, 2002.