U1 day 9 metabolism

Question 1

previous knowledge of thyroid hormones

Answer 1

Hypothalamic TRH and Pituitary TSH regulate thyroid functions, TRH is synthesized in the PVN and increases TSH secretions, TRH is composed of 3 amino acids, TSH is synthesized in the anterior pituitary by thyrotropes, TH acts via nuclear receptor

Question 2

regulation of TRH synthesis

Answer 2

integration of information from outside environment helps to regulate, such as temp, energy storage, and stress. production of beta subunit is the rate limiting step, negative feedback on thyrotropes

Question 3

TRH signaling

Answer 3

TRH neurons project to other CNS areas controlling gastric mobility, and is precent in peripheral tissues. uses a GPCR receptor, TRH-R1 and TRH-R2, TRH-R1 signals through G-alpha subunit, causing induction of PKA and Ca2+.

Question 4

Thyroid gland

Answer 4

largest endocrine organ, Secretes Thyroxine T4 and its active form T3

Question 5

T4 and T3 synthesis steps

Answer 5

exocytosis of Tg, active transport of iodine into follicular cells, oxidization of iodine and combining of Tg and iodine to form DIT or MIT. DIT + DIT = T4, DIT + MIT = T3. phagocytosis back to thyroid epithelial cells, recycling of extra iodotyronines and release of T3 and T4.

Question 6

Pendred symptom

Answer 6

mutation of transporter for cleaving Iodine transport, so can’t make T3 or T4, gets swollen thyroid, and hypothyroidism.

Question 7

Thyroid hormones transport

Answer 7

T4 is about 70 times more concentrated in blood then T3, T4 has longer half-life, so when T3 is needed, it is made from the circulating T4. They circulate bound to proteins