Table 4.

Thyroid clinical entities in the reference sample group using trimester-specific RIs derived from this study and that obtained from the assay kit literature

Trimester	Source of reference intervals	Subclinical hypothyroidism n (%)	Subclinical hyperthyroidism n (%)
First	Trimester-specific	4 (3.2)	0
	Kit literature	0	0
Second	Trimester-specific	4 (2.6)	3 (1.98)
	Kit literature	0	0
Third	Trimester-specific	2 (1.58)	5 (3.96)
	Kit literature	0	0

The different clinical entities are defined as

Normal thyroid function: TSH between reference limits and fT₄ between reference limits

Subclinical hypo-thyroidism, TSH over the upper limit of reference limits and fT₄ between reference limits

Subclinical hyper-thyroidism, TSH under the lower limit of reference limits and fT₄ between reference limits

Clinical hypo-thyroidism, TSH over the lower limit of reference limits and fT₄ under the lower limit of reference limits

Clinical hyper-thyroidism, TSH under the lower limit of reference limits and fT₄ over the lower limit of reference limits