~Teachingcenter的醫學筆記~

=Sick euthyroid syndrome (甲狀腺正能症)
-又叫做low T3 dyndrome
-當處於acute stress時，T4轉換成T3會減少，Reverse T3 (rT3) 會增加
-常見T3下降但T4和TSH正常
-但若T3和T4都下降時，為low T4 syndrome，是預後不好的情形
-補充thyroixine沒有幫助，甚至可能有害
-為一適應疾病之現象，給予治療是不必要的，治療underlying disease或治療症狀

=結節

=細針穿刺細胞學檢查
-Fine needle aspiration cytology, FNAC
-是鑑別良惡性甲狀腺結節的重要檢查
-但是對於follicular neoplasm無法分辨良惡性
-對於cystic nodule兼具治療效果

=甲狀腺癌比例
-Follicular epithelial cell
~~~Well-differentiated:
80% Papillary carcinomas
10~15% Follicular carcinomas
~~~Undifferentiated:
<1% Anaplastic carcinomas
-C cell (Calcitonin-producing)
<5% Medullary thyroid carcinoma
-Others
1~2% Lymphomas, Sarcomas, Metastasis

=Hypothalamus-Pituitary-Thyroid axis
80%的T3是由T4在周邊藉由5'-deiodinase轉換而來，20%由甲狀腺來
T4也可能由5'-deiodinase轉換成不具活性的reverse T3 (rT3)

=Thyroxine-binding globulin (TBG)，影響TBG濃度的因素
-增加(increase)：Pregnancy, neonatal state, estrogens, hyperestrogenemic states, tamoxifen, oral contraceptives, acute intermittent prophyria, infectious hepatitis, chronic hepatitis, biliary cirrhosis, genetic factors, perphenazine, HIV infection
-減少(decrease)：Androgens, large doses of glucocorticoids, active acromegaly, nephrotic syndrome, major systemic illness, genetic factor, asparaginase

=Thyrotoxicosis Periodic Paralysis (TPP)
-年輕亞洲男性最常見(2%)，非亞洲(0.2%)
-發作時鉀離子大量移入細胞中，導致血中鉀離子濃度快速下降，而發生全身癱瘓的症狀(類似hypokalemia periodic paralysis)
-常發生於早晨或傍晚，大餐後或運動後，或有其他壓力
-補充鉀離子時須謹慎，須小心反彈性高血鉀，可給予beta-blocker
-治療underlying的甲狀腺疾病可以改善