<Case Prisentation>
A 51-year-old woman was admitted to the hospital because of polydipsia and polyuria since her childhood. She needed micturation once every 1-2 hrs, even when sleeping at night. She had fallen into a pond when she was a little girl, without consciousness loss or skull fracture. In 1978, she had once lost her consciousness after she underwent a Caesarean section to deliver her second baby. She regained consciousness after massive hydration at that time, and partial diabetes insipidus was diagnosed and treated with dDAVP. The polydipsia and polyuria seemed improving, but after 10 years of treatment, she became tired to take the drug indefinitely; so she declined from her previously regular follow-up and only took medication when those bothering symptoms rebounded.

She visited our hospital in Nov 1998, because the polyuria annoyed her pretty much. According to her spectacular past history, oral dDAVP therapy was initiated. Her response to the therapy seemed to be dramatic, because the amount of her nocturnal urine output was 700 ml and 1500 ml, with and without oral dDAVP, respectively. Then she was admitted for a complete endocrine study and definite diagnosis of diabetes insipidus.

The patient was a housewife and reported to have no major systemic disease, no smoking, and drinking habits in the past. She underwent twice Caesarean sections when she was 28 and 29 year-old. Her menopausal appeared around 48~49 years old. She had no family history of DI, DM, HTN or malignancies. The body height was 140cm, weight 48.5kg. She was conscious and oriented. The temperature was 37^oC, the pulse was 70, and the respiration was 18. The blood pressure was 130/70 mmHg. Physical and neurologic examinations revealed no abnormalities. Laboratory tests were performed (Tables 1-3) .

Table 1. CBC+D/C 05/12/00

dDAVP 2μg sc injection at around 12:05pm

05/12/00 Thyroglobulin Ab 1:40, Microsomal Ab 1:20480
05/12/00 T3 121 ng/dL, T4 5.53 μg/dL
05/12/00 AC glucose 90 mg/dL, PC glucose 110 mg/dL, HbA1c 5.3%
05/12/00 ACTH 21 pg/mL, cortisol 8am 17.81 μg/dL, 4pm 8.26 μg/dL
05/12/00 DHEA-SO4 1.4 μM, hGH 0.07 ng/mL
05/12/00 LH 5.4 mIU/mL, FSH 8.8 mIU/mL, E2 <20 pg/mL
05/12/00 Prolactin 3ng/mL

Insulin hypoglycemic test on 05/19/00

Time min	Glucose AC mg/dL	HGH ng/mL	Cortisol μg/dL
0	89	0.16	8.81
15	105	0.05	7.62
30	100	0.14	9.4
60	72	0.27	15.69
120	125	0.38	19.03

 
Cranial MRI (Fig. 1&2) 05/16/00
Decreased volume of pituitary glandular tissue, without pituitary stalk thickening
The normally bright posterior lobe of pituitary gland is not found, DI is compatible
No definite mass lesion within visible brain parenchyma

After a comprehensive endocrinologic study, definite diagnosis has been obtained. DDAVP 0.1 ml intranasal bid was prescribed, and her symptoms resolved rapidly. She kept followed at our out patient department without any sequelae.

病案分析
本病例為一典型的尿崩症(diabetes insipidus)患者的臨床表現。 在鑑別診斷上, 當病患出現頻尿、夜尿或是持續口渴的情況時, 必須要排除其他造成多尿的可能原因。 當二十四小時尿量超過50c.c./kg/day, 應懷疑尿崩症(DI)的可能性。若24-h尿液的滲透壓超過300 mOsm/Kg, 必須考慮病人有solute diuresis的現象, 如控制不佳的糖尿病, 或其他較少見的會引起solute diuresis的狀況。 若病人之24-h尿液的滲透壓低於300 mOsm/Kg, 則表示有water diuresis的現象存在; 此時則應進一步評估是何種原因引起的DI。

多尿症 (polyuria)之病患的評估，包含同時測量病人的尿液與血液的滲透壓。 此時必須做限水試驗，看是否有血漿滲透壓上升, 而尿液卻仍不適當的稀釋的情況存在。 此試驗必須小心注意病人的脫水狀態。 若病人體重減少一公斤, 血漿滲透壓已顯著上升, 但尿液滲透壓卻仍維持原來的低值持續達三小時以上, 即可確定DI的診斷。 在此時給予病人vasopressin, 並於30至60分鐘後, 測量病人尿液的滲透壓。在有中樞型尿崩症的患者, 滲透壓會上升超過9%; 完全性中樞型尿崩症的患者, 滲透壓會上升超過50%以上。 若屬於腎因型尿崩症, 則不會有尿液滲透壓之上升。 腎因型尿崩症患者之治療, 包括使用利尿劑使glomerular filtration rate (GFR) 下降, 造成近端腎小管的再吸收率增加, 減少遠端腎小管的尿液傳送, 因而減少稀釋尿液之產生。 此治療必須配合鈉鹽攝取的限制, 才能達到較佳的治療效果。

本病例在打完dDAVP後之尿液滲透壓上升介於9%與50%之間, 診斷為部份型中樞性尿崩症 (partial central DI) 是恰當的。在治療上, 可給予口服chloropropamide, 或直接給予dDAVP。 DDAVP 是natural AVP的synthetic analogue, 會選擇性的作用在V2 receptors上, 根據劑量會有相關性的尿液濃縮及減少尿流量的效果。 比起natural AVP, dDAVP較不會被vasopressinase所降解, 且作用時間為natural AVP的3-4倍。 dDAVP可以經靜脈注射、 皮下注射、 鼻噴劑及口服方式給予; 一般劑量為: 皮下注射1-2μg qd或bid, 鼻噴劑10-20μg bid或tid, 口服劑型則是100-400μg bid或tid。皮下注射約15 分鐘, 口服劑型則是60分鐘左右開始作用, 出現效果。