exam deck 3 Flashcards
What regulates the release of growth hormone (GH)?
GH release is regulated by Growth Hormone-Releasing Hormone (GHRH) and Growth Hormone-Inhibiting Hormone (GHIH, or somatostatin).
Describe the release pattern of GH.
GH is released in pulses, following a circadian rhythm, with peak levels during sleep, childhood, and adolescence.
How does GH promote bone growth?
GH stimulates precursor cells in bone to differentiate into chondrocytes, which produce IGF-1; IGF-1 then stimulates chondrocytes to proliferate, forming new cartilage and bone.
What role does IGF-1 play in GH effects?
IGF-1 mediates many of GH’s growth-promoting effects, including cell division and protein synthesis, acting both locally (auto/paracrine) and as a circulating hormone.
What are the metabolic effects of GH?
GH promotes amino acid uptake for protein synthesis, breaks down fats for energy, and conserves glucose (anti-insulin effect).
How does IGF-1 contribute to GH’s metabolic effects?
IGF-1 enhances amino acid and glucose uptake into cells, providing energy and substrates for growth.
How does insulin interact with GH?
Insulin is required for growth, enhancing protein synthesis, and promoting glucose uptake into cells, which complements GH’s effects.
Why are thyroid hormones essential for GH function?
Thyroid hormones stimulate GH receptor expression, enabling GH to effectively stimulate growth.
What effect do sex hormones have on growth?
They coordinate the pubertal growth spurt, stimulate GH/IGF-1 production, and induce epiphyseal plate closure to stop growth.
What is cortisol’s role in growth?
at high levels, cortisol inhibits GH and protein synthesis, promoting protein breakdown instead, often as part of a stress response.
What causes pituitary dwarfism?
GH deficiency in childhood leads to short stature; it can be treated with hGH before epiphyseal plates close.
What is gigantism, and what causes it?
Excess GH in childhood, often due to a pituitary tumor, causing extreme height due to excessive bone growth.
What is acromegaly?
Acromegaly is caused by excess GH after epiphyseal plates have closed, leading to thickening of bones in the hands, feet, and face.
Where is the thyroid gland located, and what are its components?
The thyroid gland is located at the base of the throat, containing follicular cells that produce thyroid hormones and clear (C) cells that produce calcitonin.
What are the two main thyroid hormones, and what is their precursor?
The main thyroid hormones are T3 and T4, both derived from tyrosine and containing iodine.