Question

The growth hormone of the pituitary is more effective in:
A) Presence of thyroxine
B) Absence of thyroxine
C) Absence of insulin
D) Presence of adrenaline

Answer 1

Hint Growth hormone or somatotropin promotes the movement of amino acids into cells and the incorporation of these amino acids into proteins, thus promoting overall tissue and organ growth.
Complete Step-by-step answer:
Some hormones regulate the production and secretion of another hormone. SA hormone that has as its primary function to regulate secretion by another endocrine gland is classifieds as a tropic hormone. Like thyroid-stimulating hormone (TSH) is a tropic hormone released from the anterior pituitary. It stimulates thyroid hormone secretion by the thyroid gland.
Growth hormone effect through the mediation of a mitogen whose synthesis and release are induced by growth hormone. The mitogen is called insulin-like growth factor 1 (IGF-1). this messenger has its unique effects.
Under the influence of the growth hormone, IGF-1 is secreted by the liver, enters the blood, and functions as a hormone.
The thyroid hormone acts in synergy with GH in the development of CNS and maturation of the fetus. If thyroid hormone is absent, children show mental retardation, dwarfism, delayed puberty, and slow bone growth.
So growth hormone will be more effective in presence of thyroid hormone.
Hence the correct answer is option A.
Note: Growth hormone is released by the Growth hormone releasing factor. It is a peptide hormone produced by the hypothalamus. It is released from neurosecretory nerve terminals and carried by the hypothalamo- hypophyseal portal circulation to the anterior pituitary gland where it stimulates the synthesis and release of growth hormone. The actions of GHRH are opposed by another hypothalamic hormone, somatostatin also called the growth hormone inhibiting hormone.