endocrinology 2 Flashcards
(123 cards)
1
Q
A
2
Q
What trace element is essential for thyroid hormone synthesis?
A
Iodine
3
Q
Where are thyroid hormones stored?
A
Extracellularly in the colloid
4
Q
Which cells synthesize thyroid hormones?
A
Follicular cells
5
Q
What are the two main thyroid hormones?
A
T3 and T4
6
Q
What is the more active thyroid hormone?
A
T3
7
Q
What protein transports iodide into follicular cells?
A
NIS (sodium/iodide symporter)
8
Q
What enzyme oxidizes iodide in the follicle lumen?
A
Thyroid peroxidase (TPO)
9
Q
What is thyroglobulin?
A
A large protein that stores iodinated tyrosines for hormone synthesis
10
Q
What transporter helps secrete iodide into the follicle lumen?
A
Pendrin
11
Q
What enzyme assists TPO in oxidation reactions?
A
DUOX2
12
Q
What is the major secreted thyroid hormone?
A
T4 (~90%)
13
Q
Where is most circulating T3 produced?
A
By deiodination of T4 in peripheral tissues
14
Q
What are the main carrier proteins for thyroid hormones?
A
TBG, transthyretin (TTR), and albumin
15
Q
Which thyroid hormone has the longest half-life?
A
T4
16
Q
What enzyme family converts T4 to T3 or rT3?
A
Iodothyronine deiodinases (D1, D2, D3)
17
Q
What nutrient is essential for deiodinase activity?
A
Selenium
18
Q
Which deiodinase activates T4 to T3?
A
D2
19
Q
What is the function of D3?
A
Inactivates T4 and T3
20
Q
What is the receptor for thyroid hormones?
A
Thyroid hormone receptor (TR)
21
Q
How does unliganded TR affect gene expression?
A
Represses transcription
22
Q
How does T3-bound TR affect gene expression?
A
Activates transcription
23
Q
What type of receptor is the thyroid hormone receptor?
A
Nuclear receptor
24
Q
What condition results from iodine deficiency in early life?
A
Cretinism
25
What condition results from iodine deficiency later in life?
Goiter
26
What autoimmune disease causes hyperthyroidism?
Graves’ disease
27
What autoimmune disease causes hypothyroidism?
Hashimoto’s thyroiditis
28
What hormone controls TSH release?
TRH (thyrotropin-releasing hormone)
29
What is the source of TRH?
Hypothalamus
30
What is the effect of TSH on the thyroid gland?
Stimulates hormone synthesis and gland growth
31
What protein transports T3/T4 into blood from follicular cells?
MCT8 (monocarboxylate transporter 8)
32
33
What are the two functional parts of the pancreas?
Exocrine and endocrine
34
What are the clusters of endocrine cells in the pancreas called?
Islets of Langerhans
35
What hormone is secreted by alpha cells?
Glucagon
36
What hormone is secreted by beta cells?
Insulin
37
What hormone is secreted by delta cells?
Somatostatin
38
What hormone is secreted by PP cells?
Pancreatic polypeptide
39
What is the main function of insulin?
Lower blood glucose levels
40
What is the main function of glucagon?
Raise blood glucose levels
41
What stimulates insulin secretion?
High blood glucose
42
What inhibits insulin secretion?
Somatostatin and low glucose
43
What stimulates glucagon secretion?
Low blood glucose
44
What inhibits glucagon secretion?
High glucose and insulin
45
What is the effect of insulin on muscle?
Promotes glucose uptake and glycogen synthesis
46
What is the effect of insulin on adipose tissue?
Promotes lipid synthesis and inhibits lipolysis
47
What is the effect of insulin on the liver?
Inhibits gluconeogenesis and promotes glycogen storage
48
What is the insulin receptor type?
Receptor tyrosine kinase
49
What intracellular pathway does insulin activate?
PI3K-Akt signaling pathway
50
What transporter is responsible for insulin-mediated glucose uptake?
GLUT4
51
What is the effect of glucagon on the liver?
Stimulates glycogen breakdown and gluconeogenesis
52
What is the receptor type for glucagon?
G-protein-coupled receptor (GPCR)
53
What intracellular messenger is activated by glucagon?
cAMP
54
What second messenger pathway does glucagon use?
Gαs → adenylyl cyclase → cAMP → PKA
55
What enzyme is stimulated by glucagon to release glucose?
Glucose-6-phosphatase
56
What is the role of somatostatin in the islet?
Inhibits insulin and glucagon secretion
57
What is the incretin effect?
Oral glucose stimulates more insulin than IV glucose
58
What are the two major incretins?
GLP-1 and GIP
59
What is the effect of GLP-1?
Enhances insulin secretion and inhibits glucagon
60
What is the clinical relevance of GLP-1?
Used in type 2 diabetes treatment
61
What is the role of KATP channels in insulin secretion?
Glucose metabolism closes KATP channels, triggering insulin release
62
What is the primary stimulus for insulin gene transcription?
Increased glucose metabolism and calcium influx
63
64
What are the three major classes of steroid hormones?
Glucocorticoids, mineralocorticoids, sex steroids
65
What is the precursor molecule for all steroid hormones?
Cholesterol
66
Where are steroid hormones synthesized?
Adrenal cortex, gonads, placenta
67
Are steroid hormones stored in vesicles?
No, they are synthesized on demand
68
How are steroid hormones transported in blood?
Bound to carrier proteins like albumin or SHBG
69
Where do steroid hormone receptors reside?
In the cytoplasm or nucleus
70
What is the function of steroid hormone-receptor complexes?
Act as transcription factors
71
What is the main glucocorticoid in humans?
Cortisol
72
What is the main mineralocorticoid?
Aldosterone
73
What are the main sex steroids?
Estrogens, androgens, and progestins
74
What enzyme converts cholesterol to pregnenolone?
CYP11A1 (side-chain cleavage enzyme)
75
What enzyme is required for cortisol synthesis?
11β-hydroxylase (CYP11B1)
76
What enzyme deficiency causes congenital adrenal hyperplasia?
21-hydroxylase deficiency
77
What hormone controls adrenal steroidogenesis?
ACTH
78
How does ACTH stimulate cortisol production?
Activates cAMP/PKA pathway
79
What feedback mechanism regulates cortisol?
Negative feedback on hypothalamus and pituitary
80
What hormone stimulates aldosterone release?
Angiotensin II
81
What is the main function of aldosterone?
Promotes sodium retention and potassium excretion
82
What is the function of cortisol in metabolism?
Increases gluconeogenesis and protein catabolism
83
What is the main estrogen in premenopausal women?
Estradiol (E2)
84
What is the primary androgen produced by the testes?
Testosterone
85
What enzyme converts testosterone to DHT?
5α-reductase
86
What is the function of dihydrotestosterone (DHT)?
More potent androgen acting in skin and prostate
87
What enzyme converts testosterone to estradiol?
Aromatase
88
What hormone stimulates testosterone synthesis?
LH
89
What hormone stimulates spermatogenesis?
FSH
90
What is the role of sex hormone-binding globulin (SHBG)?
Binds sex steroids in circulation
91
Where is aromatase expressed in the brain?
Hypothalamus and amygdala
92
What is the mechanism of action of steroid hormones?
Bind intracellular receptors and regulate gene transcription
93
94
What are the two major types of bone?
Cortical and trabecular
95
What is the endocrine function of bone?
Secretion of hormones that regulate other tissues
96
What is osteocalcin?
A hormone secreted by osteoblasts
97
What is the function of undercarboxylated osteocalcin (ucOCN)?
Regulates insulin secretion and sensitivity
98
What cells produce osteocalcin?
Osteoblasts
99
What bone hormone regulates energy metabolism?
Osteocalcin
100
Which bone-derived hormone affects male fertility?
Osteocalcin
101
What is FGF23?
A phosphaturic hormone secreted by osteocytes
102
What is the main function of FGF23?
Reduces serum phosphate by increasing renal excretion
103
What organ is targeted by FGF23?
Kidney
104
What stimulates FGF23 secretion?
Increased phosphate and vitamin D
105
How does FGF23 inhibit phosphate reabsorption?
Suppresses NaPi transporters in the proximal tubule
106
What co-receptor is required for FGF23 action?
Klotho
107
What is Klotho?
A co-receptor for FGF23 and anti-aging protein
108
What enzyme is suppressed by FGF23 to reduce vitamin D?
1α-hydroxylase
109
What is the effect of FGF23 on parathyroid hormone (PTH)?
Suppresses PTH secretion
110
What bone-derived hormone is linked to muscle function?
Osteocalcin
111
What is the role of bone in the gut-pancreas axis?
Osteocalcin affects insulin and GLP-1 secretion
112
What hormone from bone increases insulin secretion?
Undercarboxylated osteocalcin
113
Which vitamin is required for osteocalcin carboxylation?
Vitamin K
114
What is the effect of insulin on osteoblasts?
Stimulates bone formation and osteocalcin release
115
What is the connection between bone resorption and osteocalcin activation?
Acidic resorption releases active osteocalcin
116
What process allows bone to sense mechanical load?
Mechanotransduction
117
What cells are involved in mechanosensing in bone?
Osteocytes
118
What is sclerostin?
A protein secreted by osteocytes that inhibits bone formation
119
What inhibits sclerostin?
Mechanical loading and PTH
120
What is the function of PTH in bone?
Stimulates bone resorption and remodeling
121
What is the endocrine role of osteocytes?
Secretion of FGF23 and sclerostin
122
Which bone-derived hormone regulates phosphate homeostasis?
FGF23
123
What is the clinical consequence of FGF23 excess?
Hypophosphatemic rickets
