Endocrine Flashcards
Steroid and thyroid hormones
lipid solubility allows passage through the membrane; have a receptor inside the cell, activate gene transcription
Non-steroid hormones (peptide and amine)
cannot pass through the membrane; have receptors outside of the cell, initiate 2nd messenger systems
Effects of the Gs pathway
ion channel activity via CNGs, gene transcription via CREs, Phosphorylation via activation of protein kinase A
hormone secretion may be controlled by
circardian rhythms, change in plasma, neurotransmitter activation, or other hormones
steroid hormones
testosterone, estradoil, progesterone
cortisol, aldosterone
(sex hormones and cortical steroids)
Amine hormones
thyroid hormones (T4), epinephrine, norpinephrine, dopamine, melatonin
what is TSH
a peptide hormone
phosphorylation may dictate
protein shape, activity stability, binding partners, or localization
blank collects hormones made by the hypothalamus; blank makes hormones under the direction of the hypothalamus
posterior pituitary, the anterior pituitary
hypothalamus
nuclei in hypothalamus produce neurohormones; delivers releasing/ inhibiting hormones; synapse to posterior pituitary and release oxytocin and ADH
Anterior Pituitary
epithelial tissue; endocrine tissue (delivers tropic hormones)
Posterior Pituitary
nervous tissue; connects to hypothalamus via infunibulum and releases oxytocin and ADH
hypothalamic-hypophysial portal system
the conduit that connects the brain to the anterior pituitary; made up of 2 capillary beds: one in the median eminence and the other in the anterior pituitary
explain the different types of hormones released at each level:
hypothalamus-> anterior pituitary -> endocrine gland
releasing/ inhibiting hormone, tropic hormone, effect hormone
TRH is a
releasing hormone
TSH is a
tropic hormone
in response to TSH- the thyroid secretes…
thyroxine, T3
Levels of negative feedback:
short loop
tropic hormone on hypothalamus
Levels of negative feedback:
long loop
effector hormone on hypothalamus and anterior pituitary
what will happen when an effector hormone is elevated in the blood
hypothalamus will produce less related releasing hormone and the pituitary will produce less related tropic hormone
thyroid follicle
secretory and functional unit of the thyroid gland
The apical side of the follicular cells faces
the lumen ( colloid)
The basal side of the follicular cells faces…
the blood
parafollicular cells release
calcitonin (lower blood calcium)
Thyroid Hormones Effects: cellular level
transcription of Na/K ATPase; increased protein synthesis, glycogen breakdown, gluconeogenesis, and fatty acid oxidation; enhanced cholesterol synthesis (LDL regulation)
Thyroid hormone effects: system level
increase BMR and heat production; synthesis of adrenergic receptors (role in BP maintanence) (permissiveness); regulator of tissue growth and development
Hyperthyroidism
Grave’s Disease: autoimmune (TSI mimics TSH); symptoms: elevated BMR, irregular rapid heartbeat, nervousness, weight loss, exophthalmos (bulging eyes)
Myxedema
adult hypothyroidism; symptoms: low BMR, feel “chilled”, edema, lethargy, mental sluggishness
Cretinism
severe hypothyroidism in infants: short, disproportionate body, mental retardation
Goiter
hypothyroidism caused by an idodine deficiency (can’t make as much thyroid hormone)
Thyroid Hormone Synthesis steps
requires Na+ and I- cotransporter, synthesis of thyroglobulin (stored in colloid), idodination of thyroglobulin, endocytosis of thyroglobulin containing T3 and T4 molecules, lysosomal enzymes release T3 and T4 from thyroglobulin
What is the role of pendrin in thyroid hormone synthesis
move I- into the colloid
TSH effects
TSH receptor activation stimulates all steps of thyroid hormone synthesis
biological effects: gene transcription (specifically for the production on Na+/I- symporter, thyroglobulin, thyroid peroxidase, thyroid hormones)
Why is TSH receptor activation important?
critical to development, growth, and function of the thyroid gland
Primary disease of the thyroid hormone
dysfunctional thyroid
secondary disease
dysfunctional pituitary and hypothalamus
A goiter is an enlargement of the thyroid gland which ofte due to the over-secretion of TSH. In which of the following pathologies will you find goiter?
primary hypothyroidism
primary hyperthyroidism
secondary hypothyroidism
secondary hyperthyroidism
primary hypothyroidism, primary hyperthyroidism; secondary hyperthyroidism
If the body makes TSI that mimic TSH (binding to the receptors). You would expect someone with Grave’s disease to exhibit…
symptoms of hyperthyroidism
would you expect someone with Grave’s disease to have a goiter
yes
