Serum Thyroxine
Serum Thyroxine: Excerpt from A Pocket Manual of Differential Diagnosis
Elevated Total Thyroxine, but Normal Free Thyroxine
Increased affinity of serum binding proteins for thyroxine (T
4)
Increased affinity of albumin for T
4
Familial dysalbuminemic hyperthyroxinemia (total T
4 and free T
4 index elevated, but free T
4 normal) (note: a familial dysalbuminemic hypertriiodothyroninemia has also been described)
Increased affinity of transthyretin for T
4
Familial increase in transthyretin binding (autosomal dominant) (total T
4 and free T
4 index elevated, but free T
4 normal)
Increased serum concentration of binding proteins for T
4
Increased T
4-binding globulin (TBG) concentration
Acute intermittent porphyria
Estrogens (including oral contraceptives, but not usual in users of low-dose pills or transdermal estrogen)
Drugs (small increases in TBG)
Clofibrate
Fluorouracil
Opiates
Perphenazine
Tamoxifen
HIV infection and AIDS
Increased endogenous estrogen production
Estrogen-secreting adrenal or testicular tumors
Pregnancy
Inherited increase in thyroid-binding globulin
Liver disease
Acute and chronic hepatitis
Biliary cirrhosis
Hepatoma
Neonatal state
Increased T
4 binding to autoantibodies to T
4
Increased transthyretin concentration
Pancreatic islet cell carcinoma
Elevated Total and Free Thyroxine
Thyrotoxicosis
Iatrogenic (excessive doses of oral levothyroxine)
Amphetamines (large doses)
Antibodies that interfere with the thyroid hormone assay
Human anti-mouse antibodies
Generalized resistance to thyroid hormone
High altitude
Inhibition of peripheral conversion of T
4 to triiodothyronine (T
3)
5' deiodinase deficiency
Drugs
Amiodarone
Oral cholecystographic agents
Iobenzamic acid
Iopanoic acid
Sodium ipodate
Tyropanoate
Propranolol (high doses) (not atenolol or sotalol)
Neonatal period
Nonthyroidal illness (including acute psychiatric illness)
Decreased Total Thyroxine but Normal Free Thyroxine
Decreased levels of serum thyroid-binding proteins
Acromegaly
Cirrhosis
Cushing's syndrome
Drugs
Androgens and anabolic steroids
Asparaginase
Chlorpropamide
Colestipol combined with niacin
Danazol
Large doses of adrenocorticotropic hormone or glucocorticoids (chronic)
Salsalate
Sulfonamides
Inherited decrease in serum levels of TBG
Malnutrition
Protein loss (e.g., nephrotic syndrome)
Nonthyroidal illness
Testosterone-secreting adrenal or ovarian tumors
Decreased affinity of serum-binding proteins for T
4
Decreased affinity of TBG for T
4
Inherited TBG that has decreased affinity for T
4
Nonthyroidal illness
Decreased affinity of transthyretin for T
4
Familial amyloidotic polyneuropathy
Nonthyroidal illness
Displacement of T
4 from serum-binding sites
Drugs
Furosemide (acutely)
Halofenate
Heparin (acutely)
Penicillin
Phenylbutazone
Salicylates (in high doses)
Other nonsteroidal antiinflammatory drugs
Fenclofenac
Meclofenamic acid
Mefenamic acid
Decreased Total and Free Thyroxine
Hypothyroidism
Functional suppression of TSH secretion
Drugs
Dopamine
Glucocorticoid excess or adrenocorticotrophic (ACTH) therapy
Nonthyroidal illness (including anorexia nervosa)
Increased hepatic metabolism of T
4 (TSH usually remains normal)
Carbamazepine
Chlorpromazine
Phenobarbital
Phenytoin
Reserpine
Rifampin
Therapy with T
3 alone
References
1. Stockigt JR: Serum Thyrotropin and Thyroid Hormone Measurements and Assessment of Thyroid Hormone Transport, pp. 387–392. See Bibliography, 4.
2. Utiger RD: Physiology, Thyrotoxicosis, Hypothyroidism and the Painful Thyroid, pp. 521–529. See Bibliography, 6.
Book Source Details
- Book Title: A Pocket Manual of Differential Diagnosis
- Author(s): Stephen N. Adler, Dianne B. Gasbarra
- Year of Publication: 1999
- Copyright Details: A Pocket Manual of Differential Diagnosis, Copyright © 1999 Lippincott Williams & Wilkins.
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