The above examples serve to illustrate the degree of variability that can be expected
when measuring plasma or serum thyroid hormones and TSH in the rat. Personal
experience of evaluating thyroid endocrine changes with compounds known to cause
thyroid follicular hypertrophy have, on occasions, been somewhat inconclusive (Davies,
1993). To minimize the difficulties associated with large inter-animal variability every
effort must be made to reduce the impact of environmental and technical variables. In
order to improve the diagnostic accuracy and consistency of thyroid hormone assessment,
a number of measures have been proposed (Davies, 1993):