以往我們所熟知的,是Octreotide,體抑素的衍生物,可以使大多數病人的生長促素和似胰島素生長因子 I 降低到正常;並且在一些病人,造成顯著的腫瘤萎縮。有效的劑量在100500ug的範圍內,皮下給予一天三次;需要長期皮下給予是一大缺點。副作用包括腹痛、脂瀉症、和膽石症。

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結果學妹拿著考題來問我:學長,為何Bromocriptine可以治療肢端肥大症呢?

Bromocriptine可以用在肢端肥大症的理由是:Bromocriptine的給予可以降低60%到80%病人的生長促素值;然而,只有一些病人可以達到生長促素值在10ng/l或以下。除此之外,Bromocriptine治療很少會減少腫瘤的大小並且只是抑制性的;當治療中斷時,生長促素過度分泌很快地會再復發。因此,Bromocriptine被當作輔助治療並用在那些生長促素值在手術或放射治療後還沒有適當地降低的肢端肥大症病人身上。

另外Cyproheptadine也可以使Gh和Prl(prolactin)減少,達到治療肢端肥大症的效果。

 

The therapeutic efficacy of the combination of cyproheptadine and bromocriptine was studied in 15 patients with active acromegaly showing incomplete GH suppression in response to bromocriptine therapy alone. The mean basal plasma GH was 31.3 +/- 5.5 micrograms/L, and it decreased to 19.0 +/- 3.9 micrograms/L during the single bromocriptine therapy (10 to 20 mg for 2 to 21 months). When cyproheptadine (12 to 16 mg for 8 to 52 months) was added to bromocriptine therapy, plasma GH decreased further (9.4 +/- 3.0 micrograms/L: vs pretreatment, P less than 0.001; vs bromocriptine treatment, P less than 0.005), and GH normalization was obtained in 8 patients. The plasma somatomedin-C levels in these 8 patients (0.3-1.8 U/ml) were within the normal range during the combination therapy. Plasma GH responses to TRH or GHRH were markedly suppressed in 6 patients during the combination therapy compared to pretreatment or during bromocriptine treatment. In addition, a clear reduction in the tumor size was observed in 4 of 7 previously untreated patients during the combination therapy. In conclusion, cyproheptadine has therapeutic efficacy in acromegalic patients who showed incomplete GH suppression in response to treatment with bromocriptine alone. Following the cyproheptadine and bromocriptine combination therapy tumor shrinkage was observed in some patients.

 

The effect of cyproheptadine on growth hormone (GH) and prolactin (Prl) secretion from cultured pituitary adenoma cells of acromegaly and pituitary gigantism was studied. When varying doses of cyproheptadine ranging from 0.01 to 1 µM were added to the incubation media, GH secretion was consistently inhibited and a dose-response relationship was observed between the cyproheptadine concentrations and the amounts of GH released into the media. In pituitary adenomas which concurrently produced and secreted Prl, cyproheptadine likewise suppressed Prl release in a dose-related manner. This effect of cyproheptadine was not blocked by coincubation with serotonin. Similarly, coincubation with a dopaminergic antagonist, haloperidol, failed to reverse the inhibitory action produced by cyproheptadine. When coincubated with dopamine, cyproheptadine further inhibited GH and Prl secretion. These results suggest that cyproheptadine possesses a direct action on human somatotroph adenoma cells to inhibit GH and Prl secretion by an unknown mechanism that is different from serotonergic and dopaminergic systems.

 

 

補充閱讀:

1.Treatment of Acromegaly with the Growth Hormone–Receptor Antagonist Pegvisomant( Volume 342 Number 16 ·1171 The New England Journal of Medicine)

 

 2.Acromegaly (Volume 355:2558-2573  December 14, 2006  Number 24  The New England Journal of Medicine)

3.The combination therapy with bromocriptine and cyproheptadine in patients with acromegaly(Endocrinol-Jpn. 1989 Jun; 36(3): 429-38 )

4.Cyproheptadine-mediated inhibition of growth hormone and prolactin release from pituitary adenoma cells of acromegaly and gigantism in culture(Acta Endocrinologica, Vol 109, Issue 4, 474-480

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