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B.

The thyroid-stimulating hormone

The name thyroid-stimulating hormone ( TSH ) has been given to a substance found in the anterior pituitary gland of all species of animal so tested for its presence.

The hormone has also been called thyrotrophin or thyrotrophic hormone.

At the present time we do not know by what biochemical mechanism TSH acts on the thyroid, but for bio-assay of the hormone there are a number of properties by which its activity may be estimated, including release of iodine from the thyroid, increase in thyroid weight, increase in mean height of the follicular cells and increase in the thyroidal uptake of Af.

Here we shall restrict discussion to those methods that appear sufficiently sensitive and precise for determining the concentration of TSH in blood.

Brown ( 1959 ) has reviewed generally the various methods of assaying TSH, and the reader is referred to her paper for further information on the subject.