Term
| How do somatropin and mecasermin differ in their effects on blood glucose? |
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Definition
Somatropin, a recombinant human GH, promotes gluconeogenesis and therefore leads to hyperglycemia.
On the other hand, mecasermin, an IGF-1 analogue, promotes hypoglycemia.
Somatropin is used in cases of pituitary dwarfism. Mecasermin is used in Laron dwarfism. |
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Term
| Why can bromocriptine and cabergoline cause nausea? |
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Definition
| These are both D2 agonists used most often in the treatment of hyperprolactinemia. Remember that D2 receptors are found in the CRTZ, and therefore stimulate this center to produce nausea. |
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Term
| What are two drugs that can be used to help slow bloodloss through ruptured esophageal varices? |
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Definition
| Vasopressin (V1 receptors) and octreotide (somatostatin analogue) both cause vasoconstriction of the portal system, reducing the bloodflow there and ultimately reducing the blood loss through esophageal varices. |
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Term
| Is desmopressin or vasopressin more active on V1 receptors of vascular smooth muscle? |
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Definition
Vasopressin is more active on V1 receptors of Vasculature. It causes vasoconstriction, especially of the splanchnic and hepatic arterioles, and is therefore useful in the Tx of bleeding esophageal varices (similar to octreotide).
Desmopressin is actually 3000x more potent at the V2 receptors of the kidney DCT and collecting duct than at V1 receptors! |
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Term
| What pituitary hormone analogue can produce a disulfiram-like reaction to alcohol? |
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Definition
Desmopressin, the vasopressin analogue, can produce a disulfiram-like reaction!
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Term
| What is the effect of somatostatin on the GIT and pancreas? |
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Definition
Somatostatin inhibits all secretions of the pancreas, stomach, and intestine!
Ex: insulin, glucagon, enzymes, gastrin, motilin, VIP, CCK, serotonin |
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Term
| Why does long term use of Octreotide produce gallstones in up to 30% of patients? |
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Definition
| Recall that octreotide is a somatostatin analogue. Like somatostatin, it inhibits the release of nearly every secretion of the GIT including CCK. Without CCK, the gallbladder is not stimulated to contract and this bile stasis favors the formation of gallstones. |
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Term
| What are therapeutic uses for octreotide? |
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Definition
Remember: octreotide is a somatostatin analogue. What does somatostatin do? It (1)blocks growth hormone release, (2) inhibits release of GIT and pancreatic hormones, and (3) causes vasoconstriction in the portal system. When would you want these effects?
1) block GH in acromegally or gigantism
2) prevent release of GIT hormones in cases of carcinoid tumors, gastrinomas, or VIPomas.
3) constrict the portal system in cases of esophageal varices due to portal hypertension! |
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Term
| Someone with hyperparathyroidism, Zollinger-Ellison syndrome, and a pituitary prolactinoma likely has what condition? |
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Definition
All of these are neoplasms of endocrine glands and are consistent with MEN 1 syndrome (aka: Wermer's Syndrome)
MEN1 = the three P's
Pituitary
Parathyroid
Pancreas |
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Term
| What is the difference between MEN 1 and MEN 2 syndromes? |
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Definition
MEN1 syndrome involves neoplasias of the parathyroid, pancreas, and Pituitary. (the 3 Ps)
MEN1 gene mutation
MEN2 syndrome involves the Thyroid, Parathyroid, and Adrenals. It is known as Sipple's Syndrome.
RET gene mutation |
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Term
| What are therapeutic uses of Somatropin? |
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Definition
| Somatropin is a recombinant growth hormone (somatotropin). It is used in conditions of insufficient GH. Such conditions include pituitary dwarfism (hypopituitarism), stimulation of growth in short children, and in Turner Syndrome to help girls achieve normal height. |
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Term
| How is prolactin release controlled? |
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Definition
Prolactin is normally under inhibitory control by dopamine acting at D2 receptors. For this reason, its release can also be inhibited by drugs that act as D2 agonists (bromocriptine), and promoted by D2 antagonists (neuroleptics, metoclopromide)!
Suckling by an infant is also stimulatory to prolactin release. |
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Term
Please explain bromocriptine's effects of:
decreased prolactin levels
nausea and vomiting
Anti-parkinsons effect |
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Definition
All of these are explainable by bromocriptine's direct agonist action at D2 receptors.
D2 receptors inhibit prolactin release from lactotrophs
D2 receptors are located in the CRTZ
Bromocriptine heps counter the decreased dopamine stimulation is found in parkinsons patients. |
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Term
| What are the main effects of oxytocin? |
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Definition
Oxytocin causes uterine contraction (which is why it is used to induce labor and also to help stop post-partum hemorrhage)
Oxytocin is also responsible for the milk-ejection reflex, in which it stimulates the myoepithelial cells around the mammary alveoli to contract, forcing milk from the glands. |
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Term
| explain the diagnostic value of desmopressin in Diabetes Insipidus. |
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Definition
Diabetes Insipidus may result from a neurogenic (central) or nephrogenic (renal) cause. If the problem is central, it means that vasopressin is not being adequately synthesized by the hypothalamus. Administration of desmopressin will improve the patient's condition because the kidney is able to respond to the now adequate levels of ADH stimulation.
However, if the diabetes insipidus is of the nephrogenic variety, it means the kidney is incapable of responding to vasopressin, so administration of desmopressin will be powerless to improve the patient's condition.
(cases of nephrogenic diabetes insipidus should be treated with thiazides or amiloride) |
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Term
| What are therapeutic uses of desmopressin or vasopressin? |
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Definition
Desmopressin is used in cases of central diabetes insipidus. It also increases the release of vWF and factor VIII, and is therefore of benefit to patients with vWF disease or hemophilia A.
Vasopressin is useful for its vasoconstrictive effect in cases of portal hypertension and bleeding esophageal varices. This vasoconstrictive effect makes it of similar value to epinephrine in terms of increased venous return during CPR |
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Term
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Definition
SIADH involves excessive vasopressin secretion. It results in hyponatremia, hypo-osmolality, hypertonic urine, total body water expansion.
It can be treated with dimeclocycline in combination with water restriction. Dimeclocycline inhibits adenylyl cyclase in the collecting ducts, thereby inhibiting the vasopressin-induced synthesis and implantation of aquaporins into the collecting duct.
Can also use conivaptan, the vasopressin antagonist |
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Term
| How do octreotide and pegvisomant differ in their effects on the GH and IGF-1 levels? |
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Definition
Octreotide, the somatostatin analogue, decreases GH levels, which also causes decreased IGF-1. Therefore octreotide decreases both GH and IGF-1
Pegvisomant blocks GH receptors, thereby decreasing IGF-1. However, the GH levels will be high because there is no feedback inhibition on GH release, and the drug itself does not inhibit GH release. So Pegvisomant causes decreased IGF-1 but increased GH levels |
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Term
| what are two important tests involving the hypothalamic-pituitary axis that you would want to carry out in a case of infertility? |
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Definition
Thyroid function and Prolactin levels should be investigated in cases of infertility.
Hyperprolactinemia and hyper or hypothyroidism can all lead to infertility. |
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Term
| What condition is conivaptan used in? |
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Definition
| Conivaptan is a vasopressin antagonist that finds use in SIADH. Remember in SIADH, vasopressin levels are too high and water is inappropriately retained, leading to hyponatremia and decreased plasma osmolality. |
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