What is the single most important determinant of basal metabolic rate (BMR)?
thyroid hormone
Which is the active form and which is the secretory form? (T3, T4)
T4 is major secretory product but T3 is most active form of hormone
What are the components of thyroid hormones?
iodide, tyrosine, thyroglobulin
Describe the multi-level control of thyroid hormone release.
TRH is released from hypothalamus; stimulates release of TSH from anterior pituitary; stimulates release of T3/T4 from thyroid gland.
Plasma thyroid hormone inhibits release of TRH and of TSH.
What is ‘permissiveness’?
Hormone-hormone interaction required for full strength of effectiveness.
E.g. Thyroid hormone stimulates synthesis of adrenergic receptors
A hyperthyroid individual has symptoms similar to a person with an adrenal medullary tumor.
T/F
True
Uncontrolled growth of the thyroid gland can result from:
A. hyperthyroid
B. hypothyroid
C. neither
D. both
both
What causes cretinism?
- Insufficient dietary iodine during pregnancy (maternal thyroid hormones limited)
- Fetal thyroid cannot manufacture sufficient T3 and T4
- Impact on CNS development (cretinism) –Formation of myelin, axon terminals, dendritic spines
What is this disease?
- Hyperthyroidism via autoimmune disease
- Produces antibodies that bind TSH receptor stimulating & not destroying receptor
- Not influenced by negative feedback from thyroxine levels
Graves disease
Acidemia is associated with high or low serum free/ionized calcium?
HIGH (more H+ bound to albumin = less spots available for calcium to bind, so more calcium in serum)
Alkalemia is associated with high or low serum free/ionized calcium?
LOW (less H+ bound to albumin = more spots available for calcium to bind, so less calcium in serum)
What are the three action sites of parathyroid hormone?
- Bone: indirect stimulation of osteoclasts
- Kidney: inhibit phosphate reabsorption & stimulates calcium reabsorption
- Intestine: indirectly stimulates calcium & phosphate absorption via stimulating renal enzyme to hydroxylate vitamin D
Which bone cells have PTH receptors?
Receptors are located on osteoblasts NOT osteoclasts
What is the effect of chronic hyperparathyroidism?
Chronic elevation of PTH leads to net bone resorption
What stimulates PTH release?
~PTH secreting cells are equipped with calcium sensors
~Hormone release usually associated with ↓ in calcium
All of calcium ingested is absorbed.
T/F
False
- Large part of calcium ingested is not absorbed
- Calcium absorption is under hormonal control
- Thus, hormonal control of absorption is major means for regulating total body calcium
- Active form of vitamin D induces synthesis of vitamin D-dependent Ca2+ binding protein
Where is calcitonin secreted from?
•Peptide hormone secreted by parafollicular cells within thyroid gland
What stimulates calcitonin secretion?
•Secretion stimulated by increased plasma Ca2+
What is the effect of calcitonin?
•Calcitonin inhibits activity of osteoclasts
