Primary abnormality of TSH secretion

Pituitary–hypothalamic disturbance

L-N

L

Central TSH excess

N-H

H

H

Very low birth weight premature infants

L-N

L

L

Thyrotoxicosis

Subclinical

U

N

N

Early treatment

U

H-N-L

H-N-L

Hypothyroidism

Subclinical

H

N

Early treatment

H

L-N

TSH assay artefact

Euthyroid subject

H

N

N

Thyrotoxic subject

L-N-H

H

H

Medications

Dopamine

L

N

Glucocorticoids

L

N