Endocrine Surgery

       HYPERPARATHYROIDISM

1. It is the most common cause of hypercalcemia among outpatients and the second most common cause in the hospital setting.
2. The three most common symptoms are fatigue, constipation, and depression.
3. The single best localization study is the sestamibi scan.
4. Persistent HPT is defined as hypercalcemia within 6 months of surgery; recurrent HPT is defined as hypercalcemia after 6 months.
5. Felix Mendl performed the first successful parathyroidectomy at the Hochenegg Clinic in Vienna. His patient was Albert, a 34-year-old tram car conductor who could not work because of severe osteitis fibrosa cystica.

·         HYPERTHYROIDISM

1. A thyroid-stimulating hormone (TSH) level is the best initial test.
2. Methimazole and propylthiouracil are the mainstays of medical treatment.
3. The two surgical options for Graves' disease are subtotal thyroidectomy and near-total thyroidectomy.
4. Johann von Mikulicz-Radecki performed the first thyroidectomy in 1885.
5. Theodor Kocher won the Nobel Prize in medicine in 1909. He was successful in reducing the high mortality rate of thyroidectomy to less than 1%. His most significant achievement was in describing postoperative hypothyroidism as cachexia strumipriva.

·         Familial hypocalciuric hypercalcemia is distinguished from primary hyperparathyroidism by a low urine calcium. Serum calcium changes approximately 0.8 mg. per dl. for every 1 gm. per dl. change in serum albumin. Thiazide diuretics can cause hypercalcemia and should not be given to patients who are hypercalcemic.

·         Acute pituitary apoplexy follows sudden hemorrhage into a pre-existing pituitary tumor or following closed head trauma. Symptoms, including headache, meningismus, and vision loss, are attributable to the intracerebral blood. Pituitary insufficiency, as well as the accompanying secondary adrenal insufficiency, may cause hypotension and shock. Other manifestations may include DI and myxedema. Acute pituitary apoplexy is a neurosurgical emergency that requires transsphenoidal decompression of the sella turcica.

·         Radioactive iodine is used only in patients who have differentiated thyroid carcinomas. It is of no value in the treatment and follow-up of patients with Hürthle cell, medullary or anaplastic carcinomas. Most papillary carcinomas are capable of taking up radioactive iodine. Most papillary carcinomas in patients under 50-years of age do so, providing that the patient has had a total thyroidectomy and there is no normal thyroid tissue to compete for the 131I. About 20% of all papillary carcinomas do not trap sufficient iodine for imaging or therapy. These are usually patients with papillary carcinoma variants: a tall cell variant of papillary carcinoma, insular carcinoma, or clear cell carcinoma.

Nearly all metastatic follicular carcinomas retain the ability to trap 131I sufficiently for imaging and for therapy. Even well-differentiated papillary and follicular carcinoma cannot compete successfully for 131I with normal thyroid tissue and unless this has been removed or subsequently ablated with an initial dose of 131I, many metastases cannot be detected or treated.

·         The principal blood supply to both parathyroid glands is the inferior thyroid artery. Parathyroid glands invariably have a single end artery supplying them, and if the main trunk of the inferior thyroid artery is ligated during thyroidectomy, there is no collateral blood supply to maintain their viability. It is preferable to divide only the branch of the inferior thyroid artery medial to those that supply either of the parathyroid glands. This requires individual clamping of smaller vessels under the thyroid sheath as these vessels penetrate into the thyroid capsule. Ligation of the main trunk of the inferior thyroid artery was commonly used for bilateral subtotal thyroidectomy in the past. It did not routinely cause hypoparathyroidism only because enough collateral blood supply was maintained to each end artery to one or more parathyroid glands. This is to be avoided.

·         Patients with marked hypercalcemia or severe symptoms should be admitted to the hospital for careful observation and monitoring. The mainstay of therapy is intravenous hydration, preferably with normal saline in sufficient quantities to maintain the urine output above 100 mL/h. These patients are often dehydrated before therapy, and fluid can be administered intravenously at a rate of 200 mL/h. Caution must be exercised in older patients who might have marginal cardiac reserve. The diuretic furosemide also increases excretion of sodium and calcium but should not be employed until the patient is well hydrated. Saline diuresis is usually effective when the hypercalcemia results from hyperparathyroidism or from a benign cause.

In contrast, the hypercalcemia of malignancy may produce severe symptoms associated with extremely high serum calcium levels that are difficult to control. In this setting, a variety of other measures may be considered. Some of the agents used to treat hypercalcemia have significant toxicity and require close monitoring. Calcitonin is a fairly weak hypocalcemic agent, but it acts rapidly and is relatively less toxic. Glucocorticoids may be particularly efficacious in patients with sarcoidosis and other granulomatous diseases. Mithramycin has proved useful in patients with hypercalcemia of malignancy, but it has a substantial cumulative toxicity (thrombocytopenia, hepatotoxicity, and nephrotoxicity). Intravenous phosphates and chelating agents have largely been abandoned because of their severe toxicity.

·          Adrenal androgens in the fetus stimulate wolffian duct development and elongate the genital tubercle. They promote midline migration of the labial folds and fusion of these folds to form the scrotum. To complete the male transformation, the urethral opening migrates to the tip of the phallus. All of these events are androgen-dependent. Since the normal female fetus does not secrete androgens, the genital tubercle, labial folds, and urethral opening all remain in the female position in this circumstance. Thus the female phenotype is associated with the absence of fetal sex hormone production. Excess androgen in the female fetus causes neonatal virilization, as is seen with congenital adrenal hyperplasia. The male infant with congenital adrenal hyperplasia is likely to have a normal appearance of the external genitalia as a neonate. Precocious puberty will develop over a period of years in this latter circumstance.

·         Pheochromocytoma associated with the MEN IIa syndrome is more often bilateral and more often malignant, therefore, abdominal exploration through an anterior approach is indicated. The ability to measure catecholamines in the plasma has made possible the clonidine suppression test. In patients without pheochromocytoma, clonidine suppresses high basal plasma concentrations into the normal range, whereas concentrations in patients with pheochromocytoma are not suppressed. Another use of plasma catecholamine measurements is in examining the ratio of 3,4-dihydroxyphenoglycol (DHPG) to norepinephrine in plasma. DHPG is released from the chromaffin cells and adrenergic neurons to a much greater extent than norepinephrine in pheochromocytoma patients compared with patients who have essential hypertension, i.e. the ratio of DHPG to norepinephrine is higher in patients with pheochromocytomas.

NP-59 (131I-6 b-iodomethyl-19-norcholesterol) is taken up as cholesterol by the adrenal cortex and is incorporated in the adrenocortical steroidogenic pathway. This is a useful agent for imaging adrenocorticol lesions. 131I-methaiodobenzylguanidine (MIBG) is a norepinephrine analogue that is useful in localizing pheochromocytomas throughout the body, especially when the tumors are multiple, extraadrenal, recurrent, or metastatic.

·         Magnetic resonance imaging (MRI) has evolved as the first choice for diagnostic imaging and is often the only tool needed to reach a therapeutic decision with regard to pituitary adenomas. With intravenous infusion of a paramagnetic substance such as gadolinium, MRI demonstrates intrasellar tumors as small as 5 mm.

·         Elevated serum prolactin levels do not always indicate the presence of a pituitary tumor. Important alternative causes are chronic renal failure, hypothyroidism, various drugs including phenothiazines, tricyclic antidepressants, exogenous estrogen, opiates, reserpine, verapamil and others. In addition, hepatic disease, pregnancy and a variety of pituitary and hypothalamic lesions cause hyperprolactinemia. If the prolactin level is over 150 ng/ml, a pituitary tumor is almost invariably the cause, but often microadenomas produce prolactin levels of less than 100 ng/ml.

·         Pituitary adenomas are the most common mass lesions in the sella turcica or parasellar region. They constitute 8% to 10% of all brain tumors. Occasionally, they are cystic and may be confused with other lesions. Craniopharyngiomas are the next most common tumor, although these are more often suprasellar in location.