ACTH (Adrenocorticotropin Hormone)
ACTH normally goes from the pituitary to the adrenal gland and produces adrenocorticosteroid hormones such as cortisol and aldosterone.
This process is regulated by negative feedback loop. (The model for all tropic hormones is regulation by a negative feedback loop.) When the pituitary senses that your cortisol and aldersoterone levels are too low, it creates ACTH to stimulate the signal to the adrenal gland to produce those hormones. Once it reaches a certain level, it shuts off the pituitary gland which then stops the signal to the adrenal gland.
If you need a physiology refresher: Review the physiology of ACTH (Including Cortisol)
Corticotropin and Cosyntropin are both ACTH-like drugs.
One potential use is to diagnose the possible cause of Addison’s disease. This is a disease of the adrenal gland where it doesn’t produce enough cortisol or aldosterone so the blood levels of these will be low. Nowadays the proper word that the textbooks want us to use is hypoglucocorticosteroidism (low levels of glucocorticosteroids).
We want to diagnose where the problem is because the problem may be in the adrenal gland (Primary adrenal insufficiency) or higher up in the body in the pituitary gland (Secondary adrenal insufficiency). Secondary adrenal insufficiency is much more common.
So what we do is we give a person an injection of these ACTH-like drugs and then we get a sample of their blood afterwards. If after the injection the cortisol levels are higher, then that means the adrenal gland reacted to the ACTH and the problem is not in the adrenal gland, but in the pituitary because the adrenals gland reacted fine. Conversely, if we give the injection and we find that the cortisol levels are unchanged, that means we have a problem in the adrenal glands.
Thyroid Stimulating Hormone (TSH)
Thyroid Stimulating Hormone (TSH) stimulates the thyroid gland to produce Thyroxine (T4). This eventually changes from T4 to T3. This process is regulated by negative feedback loop. (The model for all tropic hormones is regulation by a negative feedback loop.)
Thyrotropin (Thropar) is an injectable TSH-like drug. Thyrotropin is used to diagnose the cause of hypothyroidism. If a patient is not producing enough T4 or T3, the problem could be in the thyroid gland or the pituitary gland. If they give an injection of TSH and the T4 levels come up, that means the problem is in the pituitary. Conversely, if they get an injection of TSH and there’s no change in the blood levels, that means the problem is in the thyroid gland because it is not reacting.
Growth Hormone
This hormone, produced in the anterior pituitary, is important for children to grow. If they don’t have growth hormone they will not grow. The medication used to replace growth hormone is an injectable called Somatropen (Genotropin).
FSH, LH and Prolactin
Some other hormones in the anterior pituitary are FSH, LH and Prolactin. There are drugs that mimic both FSH and LH to treat endometriosis to stimulate progesterone production. There is no medication that mimics prolactin (oxytocin, however, does induce the production of endogenous prolactin just after birth).
