Besides stimulating the release of T3 and T4, TSH can stimulate the cell to increase production of thyroid hormones.
TSH production is stimulated by Thyrotropin-releasing hormone (TRH) which is secreted by the hypothalamus. This intern is controlled by a feedback mechanism. Increased T3 and T4 have a negative feedback mechanism on TRH as well as TSH
Tx is somewhat controversial. At the very least pt needs ipsilateral lobectomy and isthmusectomy. Some surgeons recommend total thyroidectomy. It is important to know that you don’t just take out the nodule!
LND for clinically significant nodal disease.
Surgery is followed by scanning with radioactive iodine to detect residual normal thyroid tissue as well as metastatic disease (lungs and bones).
Often have persistently high levels of calcitonin.
This often will necessitate repeated aggressive neck dissection to root out any residual tissue. However, only 38% of these patients will eventually be normalized. These patients often have occult distant mets. Laparoscopic evaluation of the liver has been recently adopted prior to neck dissection.
Note that this is a slow growing tumor and patients with incurable metastatic disease can often live for decades.
Cushing disease (pitutary ACTH excess—70% of Cushing’s syndrome)
Ectopic ACTH production-15%
Adrenal adenoma or carcinoma- 15%
Micronodular pigmented hyperplasia
Macronodular pigmented hyperplasia
Steroid dependent adrenal hypeplasia
How lesions in the pituitary, adrenal cortex and extraadrenal sites are distinguished diagnostically
First confirm that the patient has hypercortisolism.
Start with plasma cortisol on multiple venous samplings (get at 6am and 8pm)
Diurnal variation in pituitary adenomas and adrenal tumors.
Can also get 17-OH corticosteroid measurments in the urine.
Measurment of urinary free cortisol
How lesions in the pituitary, adrenal cortex and extraadrenal sites are distinguished diagnostically-CONT Plasma ACTH levels can be helpful in determining Increased Ectopic ACTH producing tumor Low or undetactable Adrenal Highly increased cortisol compared to normal NL to increased Pituitary CRH stimulation test ACTH after high dose Dexamethasone Test Plasma ACTH Level Type of Cushing’s syndrome
How lesions in the pituitary, adrenal cortex and extraadrenal sites are distinguished diagnostically-CONT
CT and MRI of head can image pituitary tumors
Ectopic Cushings syndrome represents approximately 15% of the cases and is more common in men
Most commonly oat cell ca of lung (thus chest film can be diagnostic), but can also occur with bronchial carcinoids, thymomas, and tumors of the pancreas.
CT of adrenals is a good first imaging study of the adrenals.
Other fancier tests exist
Med and surg mgmt of patients with adrenal adenoma, pituitary adenoma causing adrenal hyperplasia, and with ACTH producing neoplasm
Metyrapone and aminoglutethimide inhibit enzymes of the adrenal steroidogenic pathway. Not satisfactory for long term.
Mitotane is a chemotheraputic that is effective 30 to 70 percent of the time in decreasing steroid output in malignant functioning adrenocortical lesions.
Nonoperative treatment for congenital adrenal hyperplasia (steroid dependent)