Part 5 Flashcards
What do selenodeiodinases do?
They catalyze the conversion of T4 to T3 and T4 to reverse T3
What is more powerful, T3 or T4?
T3 is four times more powerful
True or False. The body only has thyroid receptors for T3
True
True or false. T3 is better at crossing the blood brain barrier
False. T4 is better at crossing the blood brain barrier
What are 10 things that can decrease the conversion of T4 to T3?
Beta blockers, lithium, anticonvulsants, amiodarone (but can also cause hyperthyroidism), inflammation and infections, smoking, physical and mental stress, dieting, radiation and cancer
Deficiency of what 2 nutrients can result in decreased thyroid activity?
Selenium and iodine
One grain of desiccated thyroid (60 mg) has what in it?
- 38 mcg T4
- 9 mcg T3
- Trace T1 and T2
What is the half-life of T4?
Six days
What is the half-life of T3?
18 hours
True or false. Both thyroid deficiency and severe excess can inhibit thyroid hormone production
True
Low free T3 is a strong predictor of what?
Death in cardiovascular patients
What is the most common cause of hypothyroidism globally?
Iodine deficiency
What causes hypothyroidism most often in the industrialized world?
Autoimmune disease
T3 and T4 are what percentage iodine by weight?
T3 = 59% iodine by weight T4 = 65% iodine by weight
Growth hormone stimulates the production of what in the liver?
IGF-1
Growth hormone stimulates production of what binding protein?
IGF binding protein – 3 which is associated with decreased cancer risk
True or false. Growth hormone worsens carotid atherosclerosis
Faults. It inhibits carotid atherosclerosis
True or false. Growth hormone deficiency is associated with increased cardiovascular mortality
True
IGF-1 has what effect on the nerves in the brain?
It has cytoprotective effects against beta-amyloid plaque formation and it increases dendritic formation of cortical neurons
What is the best serum marker of growth hormone levels?
IGF – 1
How is testosterone associated with memory and dementia?
Low levels are associated with impaired memory and an increased risk for dementia
True or false. Men with low testosterone die 88% later then men with high testosterone
False. Men with low testosterone die 88% sooner than men with high testosterone
True or false. The lower the free testosterone the more likely coronary artery disease will be present
True
Name three things that testosterone replacement will do to improve cardiac function
1) it improves ST depression
2) it dilates coronary arteries
3) it increases cardiac output
Female:Male Testosterone levels
1:10
Why is testosterone therapy anti-inflammatory?
It prevents cytokine production and prevents the formation of VCAMS
What does testosterone therapy do to the skeletal system?
It prevents bone loss
How does testosterone replacement therapy help a person to feel better?
It improves sense of emotional well-being, self confidence and motivation
Two routes of aromatization via aromatase (CYP 19)
Androstenedione to estrone
Testosterone to estradiol
What 6 things increase aromatization?
Obesity, alcohol and decreased zinc
Stress, inflammation and insulin resistance
What four things decrease aromatization?
Zinc supplementation, weight-loss, chrysin and anastrozole
Does chrysin decrease aromatization in vivo?
No, only in Vitro
What is another name for anastrozole?
Arimidex
Gonadotropin Releasing Hormone stimulates what and releases what?
It stimulates the anterior pituitary and releases FSH and LH
FSH stimulates and produces what?
It stimulates the Sertoli cells and produces sperm
LH stimulates what produces what?
It stimulates the Leydig cells produces testosterone
