F00574 020 f003

Tyrosinc

HO O ch₂-ch-cooh

ł

NH,

Monoiodotyrosine (MIT)

I    nh₂

o ch₂-ch-cooh

HO

Diiodotyrosine (DIT)

HO-/ VcH₂-CH-COOH

i'

$

Triiodothyronine (T₃)

I_ I_    NH;

HOO-^^-CHj - Ćh - COOH

I

Thyroxine (T₄)

i    i

nh₂

^H°~0~°~0~^cHa~^^H~^cooH I⁷ I⁷

r~

Follicular

epithelium

Red blood cells

Negative

feedback

FreeT_4lT₃‘

(<1%)

Protein-bound T₄. T₃ (>99%)

Parafollicular (C) cclls

Colloid

Reverse T₃ (rT₃)

i

nk₂

HO -0-0^, -CH-COOH

Target tissues

	Increased metabolic ratę
c	Mimie {S-adrenergic action,
	e.g. on heart ratę. gut motility
^4 *	CNS activation
	Bonę demineralisation
L>T3^/	Cellular differentiation
V	^etc. ,

I_L

© Elsevier. Boon et al.: Davidson's Principles and Practice of Medicine 20e - www.studentconsult.com