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Based on mechanism of action, the hormones may
be classified into two which are?
Group I. Hormones with cell surface receptors
Group II. Hormones with intracellular receptors.
Stimuli for inhibiting the secretion hypothalamic TRH
high T3 & T4
Colloid
Membrane receptors:
Intracellular receptors ( Cytosolic/Nuclear)
Pituitary gland is removed and transplanted to other part of the body?
Rate of secretion is very low
❖Hormones are synthesised in the cell body at the
hypothalamus
❖Transported in combination with “carrier” proteins called neurophysins down to the nerve ending in the posterior pituitary gland
❖Require several day to reach the gland
A child shows the following symptoms: deficient growth; failure to show sexual development; decreased ability to respond to stress.
What is the most likely cause of all these symptoms?
Destruction of the anterior pituitary or hypothalamus. These symptoms reflect the absence of, in order, growth hormone, the gonadotropins, and ACTH (the symptom is due to the resulting decrease in cortisol secretion). The problem is either primary hyposecretion of anterior pituitary hormones or secondary hyposecretion because the hypothalamus is not secreting hypophysiotropic hormones normally.
Pituitary stalk is cut above the pituitary gland but the entire hypothalamus is left intact?
Transient decrease for a few days. Posterior pituitary hormones continue to be secrete normally by the cut end of the fibers within the hypothalamus
❖Hormones are synthesised in the cell body at the
hypothalamus
❖Transported in combination with “carrier” proteins called
neurophysins down to the nerve ending in the posterior
pituitary gland
❖Require several day to reach the gland
A person is receiving very large doses of a cortisol like drug to treat her arthritis.
What happens to her secretion of cortisol?
The high dose of the cortisol-like substance inhibits the secretion of ACTH by feedback inhibition of (1) hypothalamic corticotropin releasing hormone and (2) the response of the anterior pituitary to this hypophysiotropic hormone. The lack of ACTH causes the adrenal to atrophy and decrease its secretion of cortisol.
A person with symptoms of hypothyroidism (for example, sluggishness and intolerance to cold) is found to have abnormally low plasma concentrations
of T4, T3, and TSH. After an injection of TRH, the plasma concentrations of all three hormones increase. Where is the site of the defect leading to the
hypothyroidism?
The hypothalamus. The low basal TSH indicates either that the pituitary is defective or that it is receiving inadequate stimulation (TRH) from the hypothalamus. If the thyroid itself were defective, basal TSH would be elevated because of less negative-feedback inhibition by TH. The TSH increase in response to TRH shows that the pituitary is capable of responding to a stimulus and so is unlikely to be defective. Therefore, the problem is that the hypothalamus is secreting too little TRH.
Histology of thyroid gland
Explain the pyramidal lobe of thyroid gland
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