TSHR and Primary hypothyroidism: Our experimental approach, which included a newly developed, highly sensitive sandwich ELISA for longitudinal assessment of mouse TSH microfractions of tail-tip whole blood, allowed us to decipher acute pulse patterns of TSH secretion in euthyroid freely moving mice; their changes in a mouse model of primary hypothyroidism; and their high efficiency at stimulating the thyroid, both at the level of cAMP production due to TSH receptor stimulation and T4 levels into bloodstream.