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Drugs affecting anterior pituitary, Somatostatin, Octreotide, Mecasermin,…
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Somatostatin
It is secreted by hypothalamus, GIT as well as by delta cells of pancreas.
It inhibits the secretion of GH, TSH, prolactin, insulin, glucagon, gastrin and Hcl.
it causes vasoconstriction of hepatic, splanchnic and renal blood vessels and can be used for bleeding peptic ulcer.
due to reduced gastric acid secretion and reduced mucosal blood flow.
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Adverse effects are nausea, dyspepsia, achlorhydria, steatorrhea and diarrhea mainly in diabetic autonomic neuropathy.
Octreotide
it is more potent, long acting and most widely used.
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it is preferred agent over somatostatin for acromegaly and other hormone secreting tumours like gastrinoma, carcinoid syndrome, glucagonoma, VIP secreting adenomas (secretory diarrhea) and diabetic diarrhea.
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Slow release microsphere formulation of octreotide acetate is a depot preparation, very long acting and administered 20-40mg IM once in a month in case of acromegaly.
Mecasermin
Mecasermin is a complex of recombinant human IGF-1(insulin like growth factor-1) and IGF-binding protein-3.
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GH receptor antagonist
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it normalizes the level of IGF-1 almost in all the cases of acromegaly including small pituitary adenomas and useful for the cases not responding to other treatment.
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Prolactin
The increased level of prolactin (hyperprolactinaemia) inhibits the release of gonadotropins and response of gonadotropins to ovaries.
And therefore, often ovulation does not take place during the breast feeding and possibly as long as breast feeding is continued.
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this implies that continuous secretion of PRL during breast feeding acts as a natural contraceptive mechanism.
This is also the explanation for the infertility in women with pathological hyperprolactinemia and correction of prolactin level often results into fertility.
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Gonadotropins
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Both the gonadotropins, the FSH and LH act on gonads and cause the release of gonadal hormones that promote the gametogenesis in both the males and females.
Moreover, FSH and LH also directly help in the gametogenesis.
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GnRH analogues
GnRH analogues like busurelin, goserelin, leuprolide, nafarelin, deslorelin, triptorelin and histrelin are more potent and longer acting than natural GnRH.
These drugs stimulate gonadotropin secretion when given in a pulsatile manner whereas inhibit the release on continued administration.
Therefore these agents can be used in pulsatile manner for the treatment of anovulatory infertility, hypogonadotropic hypogonadism, delayed puberty and cryptorchidism.
These conditions require excess of gonadotropins for treatment.
On the other hand, if given continuously reduction in gonadotropin secretion is seen that is beneficial in conditions like precocious puberty, endometriosis, prostatic carcinoma, PCOD and uterine fibroids.
GnRH antagonists
Cetrorelix, ganirelix, abarelix and degarelix
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Another use of these drugs is controlled ovarian stimulation in invitro fertilization.
In this process, recombinant FSH is given to prepare the ova for ovulation induction.
Constant monitoring of serum estradiol is done and when sufficient levels are reached,
GnRH antagonists are given to prevent premature follicular luteinization before induction of ovulation as they are used to suppress the LH surge.
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Breast engorgement
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However, this practice is not preferred due to risk of side effects
In females
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Gonadotropins are used in cases of anovulatory not responding to clomiphene or in cases of polycystic ovaries.
Menotropin (FSH 75IU + LH 75IU) IM is given once a day for about 10 days followed by HCG 5000-10000 IU and this results in ovulation within 24-48 hours in most cases.
- Cryptorchidism/Cryptorchism (undescended testis)
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HCG is used in a dose of 1000-2000IU IM twice or thrice a week till testis descent to a maximum duration of 2-4 weeks and if descent doesn't occur, surgery is performed (orchidopexy).
Sermorelin
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used for diagnostic purpose to differentiate whether dwarfism is due to pituitary disease or hypothalmic disease.
Clonidine (low dose)
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As it may increase GH release though benefit is doubtful particularly if GH secretion is within normal range.
Somatostatin analogues
Octreotide, Lanreotide, Vapreotide, Seglitide
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Bromocriptine or cabergoline are preferred and can be considered first line agents for this purpose.
The intravaginal administration (vaginal tablets) of bromocriptine and cabergoline leads to early achievement of peak concentration.
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In males
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It is treated by administration of HCG 1000-2500 IU IM 2-3 times a week for 2-3 months followed by menotropin (FSH 75IU + LH 75IU) IM thrice a week for 4-6 months.
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Cosyntropin
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used for diagnostic purpose to differentiate congenital adrenal hyperplasia from ovarian hyperandrogenism and to detect adrenal insufficiency.
Hormones
Hormones are the substances which are produced by specific cells in the body and act away from their site of production.
These are produced by endocrine glands.
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Dopamine
Dopamine increases GH release in normal subjects but decreases it in acromegalics.
Best response with dopamine agonists is seen in patients secreting both GH and prolactin.
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Fundoscopic examination of children is recommened at initiation of GH therapy and at periodic intervals
because rarely GH therapy is associated with intracranial hypertension with papilledema, visual changes, headache and vomiting.
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Macimorelin acetate
it is a growth hormone (GH) receptor agonist approved to be used for the diagnosis of adult growth hormone deficiency.
Dopaminergic agonists
Bromocriptine, cabergoline, pergolide and quinagolide
Infertility
Hyperprolactinemia inhibits the action of gonadotropins and correction of hyperprolactinemia often leads to pregnancy provided other parameters are normal.
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Cabergoline
Cabergoline is a longest acting dopamine agonist(ergot derivative) that is better tolerated than bromocriptine.
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- To facilitate in vitro fertilization
Maturation of several ova at a time can be induced by menotropin and timing of ovulation can also be controlled by using menotropin (FSH + LH).
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- Hypogonadotropic hypogonadism and infertility
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