RT Book, Section
A1 Blake, Elizabeth W.
A2 Sutton, S. Scott
SR Print(0)
ID 1158316462
T1 Thyroid Disorders
T2 McGraw-Hill's NAPLEX® Review Guide, 3e
YR 2019
FD 2019
PB McGraw-Hill Education
PP New York, NY
SN 9781260135923
LK accesspharmacy.mhmedical.com/content.aspx?aid=1158316462
RD 2022/05/16
AB The  thyroid  gland  is  located  in  the  front  of  the  neck  and  operates  via  negative  feedback  to  synthesize  thyroid  hormones.  The  hypothalamus  produces  thyrotropin-releasing  hormone  (TRH)  which  stimulates  the  pituitary  to  release  thyroid-stimulating  hormone  (TSH).  TSH,  also  known  as  thyrotropin,  stimulates  the  synthesis  and  release  of  thyroid  hormones  from  the  thyroid  gland.  Formation  of  thyroid  hormones  requires  iodination  of  tyrosine  residues  by  thyroid  peroxidase  to  produce  monoiodinated  and  diiodinated  residues  that  couple  to  form  triiodothyronine  (T3)  and  levothyroxine  (T4).  Circulating  levels  of  T3  and  T4  regulate  TSH  secretion  via  negative  feedback.  The  thyroid  gland  is  responsible  for  the  production  of  T4  and  less  than  20%  of  T3.  Peripheral  conversion  of  T4  to  T3  forms  the  majority  of  T3.  Compared  to  T4,  T3  is  more  potent,  less  bound  to  plasma  proteins,  and  has  a  shorter  half-life.  Thyroid  hormones  affect  multiple  organ  systems  throughout  the  body  and  alterations  in  hormone  concentrations  and  TSH  lead  to  hyper-  or  hypothyroidism  (Tables  62-1  and  62-2).