Pituitary gland and thyroid gland Flashcards
What is the hypothalamus-pituitary-end-organ axes?
Hypothalamus in the brain secretes cortisol releasing hormone (CRH - clinically measured) to the anterior pituitary gland. Then the pituitary gland secretes hormones that affect end organ systems (liver, adrenal cortex, thyroid gland)
List 4 anterior pituitary gland hormones, and their hypothalamic control hormones.
1) Growth hormone (GH). Hypothalamic control = Growth hormone releasing hormone (GHRH), somatostatin (-). Effect is growth
2) Adrenal corticotrophic hormone (ACTH). Hypothalamic control = cortisol releasing hormone (CRH). Effect is on adrenal cortex
3) Thyroid stimulating hormone (TSH). Hypothalamic control = thyrotropin-releasing hormone (TRH), somatostatin (-). Effect is on thyroid.
4) Prolactin (PRL). TRH. Effect is on lactation.
somatostatin = growth hormone inhibiting hormone
List 3 effects of thyroid hormones.
1) Metabolism: Increase matabolic rate, increase catabolism, increase heat generation
2) Nervous system: Increase sensitivity to sympathetic nervous system by increased epinephrine receptors. Increase heart rate, ventilation rate. Increase neuronal activity.
3) Development and differentiation: Brain (neurons), long bone growth.
How is the growth hormone signaling pathway related to the insulin signaling pathway?
Target cells: Virtually every cell in the body. Mediated through GH and IGF receptors.
Insulin like growth factor-1 (IGF1) is produced in the liver by GH signaling. Both ligand and receptor share homology to insulin signaling. Most metabolic functions of GH are also mediated through IGF-1.
How does modulating growth hormone signaling affect longevity?
GH/IGF-1 as anti-aging therapeutics: Positive effects on body composition (muscle, BMI, skin), but more risk than benefits
GH/IGF-1 suppression for anti-aging: Increase lifespan in mice and C elegans. Caloric restriction might have similar effect through mTOR.
Describe the pathway for hormone secretion from the liver.
Growth hormone receptor (GHR) dimerizes with growth hormone (GH) on the plasma membrane
GHR associated kinases (such as JAK2) are activated.
Activated signaling cascade produces IGF-1
What are the symptoms of hyper- and hypothyroidism?
Hyperthyroidism: Metabolic symptoms (weight loss, heat intolerance, fatigue) and nervous symptoms (palpitation, irritability, tremor)
Hypothyroidism: Fatigue, iodine deficiency, thyroiditis, swollen and puffy skin (myxedema)
Interpret the results of simple thyroid function tests (TFTs).
Thyroid function tests refers to a series of blood tests designed to test thyroid function.
TSH: Most sensitive. Increase means hypothyroidism. Decrease means hyperthyroidism.
Free T4: Reflects thyroid function.
Free T3: T4 may appear normal in some hyperthyroidism (normal T4, increase T3, decrease TSH)
T/F: Primary target organs of anterior pituitary gland hormones are secretary glands.
True
T/F: All of the anterior pituitary gland hormones are peptide hormones.
True
T/F: Mutations in the components of the IGF-1 signaling pathway can cause cancers.
True
T/F: Increase in serum TSH level in a patient indicates primary hyperthyroidism but not secondary hyperthyroidism.
False
