I

I

I

I

HO

5’

5

HO

HO

Tyr

Tyr

HO

O

Tyr

Tyr

NH2

3’

3

NH2

I

I

I

I

4

Thyroglobulin

Thyroglobulin

3,5,3’5’-tetraiodothyronine

Coupling of iodotyrosine moities results in the loss  of  the peptide linkage to thyroglobulin allowing thyroid  hormones to diffuse across the cell membrane

I

3,5,3’-Triiodothyronine

I

+

Tyr

HO

Tyr

HO

O

Tyr

Tyr

NH2

NH2

I

I

T

I

I

3

Thyroglobulin

Thyroglobulin