促腎上腺皮質素 (ACTH)
促腎上腺皮質素 (ACTH) 是一種由腦下垂體前葉分泌的 39 個胺基酸多肽荷爾蒙。在獸醫學中，它主要作為**診斷劑**，用於評估腎上腺功能。 - **主要用途**：ACTH 刺激試驗用於診斷腎上腺皮質機能低下（愛迪生氏症）、識別醫源性腎上腺皮質機能亢進（庫興氏症候群），以及監測抑制腎上腺治療（如 mitotane 或 trilostane）的效果。 - **限制**：與低劑量地塞米松抑制試驗 (LDDST) 相比，作為犬隻自然發生之庫興氏症候群的篩檢工具，其敏感度較低。 - **臨床重點**：由於天然豬 ACTH 凝膠產品成本高、取得不易且效力不一，目前現代臨床實務中進行 ACTH 刺激試驗時，多偏好使用合成的 **cosyntropin**。
作用機制: Endogenous ACTH release is controlled by corticotropin-releasing factor (CRF) from the hypothalamus and is subject to negative feedback by glucocorticoids. Exogenous corticotropin binds to **melanocortin-2 receptors (MC2R)** in the **zona fasciculata** of the adrenal cortex $\rightarrow$ stimulates the conversion of cholesterol to pregnenolone via cholesterol desmolase $\rightarrow$ rapidly increases the synthesis and release of **glucocorticoids** (primarily **cortisol** in mammals and **corticosterone** in birds and reptiles).
各物種劑量
- ACTH Stimulation Test · 2.2 Units/kg IM · IM · Once · Draw baseline blood sample, administer gel, then draw samples at 60 minutes and 120 minutes after injection.
- ACTH Stimulation Test · 0.5 Units/kg IM · IM · Once · Draw baseline blood sample, administer gel, then draw sample 120 minutes after injection.
- ACTH deficiency or primary bovine ketosis · 200-600 Units initially followed by daily or semi-daily dose of 200-300 Units · IM · daily or semi-daily
- ACTH Stimulation Test · 1 Unit/kg IM · IM · Once · Draw baseline blood sample, administer gel, then draw second sample 8 hours later.
- ACTH Stimulation Test · 1 Unit/kg IM · IM · Once · Administer between 8 and 10 AM; take post ACTH cortisol levels at 2 and 4 hours post dose.
- ACTH Stimulation Test · 16-25 Units IM · IM · Once · Draw baseline blood sample for corticosterone (not cortisol), administer IM, draw second sample 1-2 hours later.
- ACTH Stimulation Test · 2.2 Units/kg IM · IM · Once · Draw baseline blood sample, administer gel, then draw second sample 120 minutes after injection.
給藥途徑
禁忌症
- Hypersensitivity to porcine proteins
- Intravenous (IV) administration of the repository gel formulation
不良反應
- Fluid and electrolyte disturbances (with prolonged/chronic use)
- Hypersensitivity reactions (rare)
藥物相互作用
- Anticholinesterases (e.g., pyridostigmine) · May antagonize effects in patients with myasthenia gravis
- Diuretics · May increase electrolyte loss (e.g., hypokalemia) if used chronically
- Glucocorticoids (hydrocortisone, cortisone) · Exogenous administration on the day of the test will cross-react with cortisol assays and invalidate test results
監測
- Serum cortisol levels (pre- and post-injection for mammals)
- Serum corticosterone levels (pre- and post-injection for birds/reptiles)
- Electrolytes and fluid balance (only if used chronically)
過量
When used for diagnostic purposes, acute inadvertent overdoses are highly unlikely to cause any significant adverse effects. Monitor the patient as required and treat symptomatically if necessary.
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