Exam 3 Endocrine System Flashcards
What type of hormone is Vitamin D?
steroid
What is the second step in steroid synthesis?
pregnenolone
What are the 3 primary classes of steroid hormone?
- mineralocorticoids
- glucocorticoids (cortisol)
- sex hormones (chiefly androgens)
Where are steroid hormones produced?
- synthetic enzymes are in mitochondria and SER
- chiefly in gonads and adrenal cortex
- but may also be produced in adipose tissue, liver, and skin
All peptides are unbound except-
IGF and about 1/3 of GH
What hormones use the PKA pathway?
- Pituitary hormones (ACTH, FSH, LH, TSH)
- catecholamines
- Glucagon
- Calcitonin
- PTH
What hormones use the PLC pathway?
- Hypothalamic hormones (TRH, GnRh, oxytocin, ADH)
- Catecholamines
What is the 2nd messenger in the PLC pathway?
- IP3
- then calcium
In the PLC pathway, ___ triggers release of calcium from the ____.
IP3; ER (or mitochondria in the anterior pituitary)
List the sequence of molecules activated in the PKA pathway before phosphorylation cascade.
1) receptor
2) G-alpha-s subunit
3) adenylate cyclase
4) cAMP
5) Protein kinase A
List the sequence of molecules activated in the PLC pathway before the release of calcium.
- receptor
- g protein subunit
- Phospholipase C
- IP3
Kinases phosphorylate proteins at which amino acids?
- serine
- threonine
- tyrosine
What are 3 ways kinases can be activated?
- hormones if receptor is also a kinase
- second messengers
- other kinases (cascades)
What is a response element?
specific regions of DNA that proteins bind to modify transcription
Which hormones use the tyrosine kinase signaling pathway?
- most growth factors e.g. IGF and epidermal growth factor (EGF)
- GH and insulin use a variant
What is the pathway of hypothalamic hormones to the anterior pituitary?
ventral hypothalamus> parvocellular neurons> hypothalamic hypophyseal portal system>endocrine cells of anterior pituitary
What is the pathway of hypothalamic hormones to the posterior pituitary?
hypothalamic nuclei> magnocellular neurons> hypothalamic hypophyseal tract
What hormones are secreted from the anterior pituitary?
- TSH
- FSH
- GH
- ACTH
- prolactin
- LH
CRH stands for
corticotropin-releasing hormone
TRH stands for
thyrotropin-releasing hormone
GnRH stands for
gonadotropin-releasing hormone
PRF and PIH stand for
- prolactin-releasing factor
- prolactin-inhibiting hormone
What is the abbreviation for prolactin?
PRL
Name all the hypothalamic hormones.
- GnRH
- GH-RH
- GH-IH
- PRF
- PIH
- TRH
- CRH
Name the primary hormones.
- androgens
- estrogens, progesterone
- cortisol
- thyroid hormones
- IGFs
what is somatostatin?
GH-IH
What is somatotropin?
GH-RH
What is somatomedin?
IGF-1
What processes does growth hormone upregulate?
- fat oxidation and lipolysis
- gluconeogenesis and glycogenesis
- insulin resistance
- insulin secretion in the pancreas
What processes does growth hormone downregulate?
- glucose uptake from muscle and fat
- lipogenesis in fat
What pathway does growth hormone use?
tyrosine kinase pathway
In terms of feedback, what will happen if IGF levels are elevated?
GH-IH levels will increase, in turn lowering GH levels
What are two potential meanings of elevated TSH levels?
- thyroid hormone level could be is low (hypothyroidism)
- less commonly, TRH levels are high
What hormone classification are thyroid hormones? Are they hydrophilic or lipophilic? How do they enter the cell and where do they bind?
- they are amines
- they are lipophilic
- they use a transporter
- they bind to nuclear receptors
What is the function of CREB signaling pathways?
regulate transcription
What pathway enduces exocytosis of TSH?
PLC
What pathway enduces synthesis of T3 and T4?
PKA
What is the difference between Tg and TBG?
- Tg is precursor for T3 and T4
- TBG binds t3 and T4
Thyroid receptors heterodimerize with-
retinoic acid receptors (RXR)
What are the manifestations of hypothyroidism?
- Hair loss
- Goiter
- reduced HR
- constipation
What are the manifestations of hyperthyroidism?
- Hair loss
- bulging eyes
- Goiter
- palpitations
- diarrhea
What is the pathway for iodine from the blood to the pendrin transporter?
- “trapping” by sodium-dependent transporter into follicle cell
- “activation” of iodine molecule and transepthelial diffusion to pendrin
In TH synthesis, what happens in the colloid once iodine enters?
- Organification: thyroperoxidase (TPO) attaches iodine to Tg by means of H202 forming regions of 3 (MIT) & 4 (DIT) iodides
- Modified Tg gets endocytosed back into follicle cell by pendrin transporter
What happens once modified Tg is transported back into follicle cell from colloid?
- lysozyme cleaves it into 6 molecules of T3 or T4 (variable combination)
- T3 and T4 released into general circulation, bound to TBG or albumin
Which hormones cannot use PLC or PKA pathway?
steroids, but some can use CREB
