Michael T. Sheehan

Preliminary Comparison of the Endoscopic Transnasal vs the Sublabial Transseptal Approach for Clinically Nonfunctioning Pituitary Macroadenomas

OBJECTIVE To assess the advantages and disadvantages of an endoscopic transnasal approach to pituitary surgery for a select group of clinically nonfunctioning macroadenomas and to compare results of this approach with the sublabial transseptal approach at a single institution. PATIENTS AND METHODS We retrospectively reviewed the records of 26 patients with clinically nonfunctioning pituitary macroadenomas approached endoscopically and 44 matched control patients with the same tumors approached sublabially between January 1, 1995, and October 31, 1997. RESULTS At baseline, the groups were not significantly different for age, sex distribution, number of comorbid conditions, visual field defects, degree of anterior pituitary insufficiency, or preoperative assessment of tumor volume or invasiveness. Mean (SD) operative times were significantly reduced in the endoscopic group vs the sublabial group: 2.7 (0.7) hours vs 3.4 (0.9) hours (P < .001). Postoperative assessment of surgical resection and postoperative alterations of anterior pituitary function or visual fields were not significantly different between groups, and complication rates were similar in both groups. CONCLUSION This endoscopic transnasal approach to pituitary resection results in significantly shorter operative time without compromising the extent of tumor resection. The distinct disadvantage of this approach is an off-center view of the sella and a diminished working channel to the sella turcica. For these reasons, the endoscopic approach or its variation is an alternative to the sublabial approach but should be considered only by experienced pituitary neurosurgeons.

Relationship between plasma free fatty acid, intramyocellular triglycerides and long-chain acylcarnitines in resting humans

We hypothesized that plasma non‐esterified fatty acids (NEFA) are trafficked directly to intramyocellular long‐chain acylcarnitines (imLCAC) rather than transiting intramyocellular triglycerides (imTG) on the way to resting muscle fatty acid oxidation. Overnight fasted adults (n= 61) received intravenous infusions of [U‐13C]palmitate (0400–0830 h) and [U‐13C]oleate (0800–1400 h) labelling plasma NEFA, imTG, imLCAC and im‐non‐esterified FA (imNEFA). Two muscle biopsies (0830 and 1400 h) were performed following 6 h, overlapping, sequential palmitate/oleate tracer infusions. Enrichment of plasma palmitate was ∼15 times greater than enrichment of imTG, imNEFA‐palmitate and im‐palmitoyl‐carnitine. Fatty acid enrichment in LCAC was correlated with imTG and imNEFA; there was a significant correlation between imTG concentrations and imLCAC concentrations in women (r= 0.51, P= 0.005), but not men (r= 0.30, P= 0.11). We estimated that ∼11% of NEFA were stored in imTG. imTG NEFA storage was correlated only with NEFA concentrations (r= 0.52, P= 0.004) in women and with (r= 0.45, P= 0.02) in men. At rest, plasma NEFA are trafficked largely to imTG before they enter LCAC oxidative pools; thus, imTG are an important, central pool that regulates the delivery of fatty acids to the intracellular environment. Factors relating to plasma NEFA storage into imTG differ in men and women.

Metabolic complications of obesity. Pathophysiologic considerations.

Given a specific research interest in human fatty acid metabolism, this article focuses primarily on the evidence surrounding the hypothesis that dysregulation of the fuel release function of fat cells (lipolysis) is an important contributing factor to the health hazards of obesity.

Biochemical Testing of the Thyroid: TSH is the Best and, Oftentimes, Only Test Needed – A Review for Primary Care

Disorders of thyroid function are common, and screening, diagnosis, and management are often performed by primary care providers. While management of significant biochemical abnormalities is reasonably straight forward, laboratory tests only slightly outside, or even within, the normal range are becoming more difficult to appropriately manage. A large part of this increasing difficulty in appropriate management is caused by patients requesting, and even demanding, certain tests or treatments that may not be indicated. Symptoms of thyroid dysfunction are non-specific and extremely prevalent in the general population. This, along with a growing body of information available to patients via the lay press and internet suggesting that traditional thyroid function testing is not reliable, has fostered some degree of patient mistrust. Increasingly, when a physician informs a patient that their thyroid is not the cause of their symptoms, the patient is dissatisfied and even angry. This review aims to clarify the interpretation of normal and mild abnormalities of thyroid function tests by describing pituitary-thyroid physiology and through an in depth review of, arguably, the three most important biochemical tests of thyroid function: TSH, free T4, and anti-TPO antibodies. It is important for primary care providers to have an understanding of the shortcomings and proper interpretation of these tests to be better able to discuss thyroid function with their patients.

Hyperinsulinemia and skeletal muscle fatty acid trafficking

We hypothesized that insulin alters plasma free fatty acid (FFA) trafficking into intramyocellular (im) long-chain acylcarnitines (imLCAC) and triglycerides (imTG). Overnight-fasted adults (n = 41) received intravenous infusions of [U-¹³C]palmitate (0400-0900 h) and [U-¹³C]oleate (0800-1400 h) to label imTG and imLCAC. A euglycemic-hyperinsulinemic (1.0 mU·kg fat-free mass⁻¹·min⁻¹) clamp (0800-1400 h) and two muscle biopsies (0900 h, 1400 h) were performed. The patterns of [U-¹³C]palmitate incorporation into imTG-palmitate and palmitoylcarnitine were similar to those we reported in overnight postabsorptive adults (saline control); the intramyocellular palmitoylcarnitine enrichment was not different from and correlated with imTG-palmitate enrichment for both the morning (r = 0.38, P = 0.02) and afternoon (r = 0.44, P = 0.006) biopsy samples. Plasma FFA concentrations, flux, and the incorporation of plasma oleate into imTG-oleate during hyperinsulinemia were ~1/10th of that observed in the previous saline control studies (P < 0.001). At the time of the second biopsy, the enrichment in oleoylcarnitine was <25% of that in imTG-oleate and was not correlated with imTG-oleate enrichment. The intramyocellular nonesterified fatty acid-palmitate-to-imTG-palmitate enrichment ratio was greater (P < 0.05) in women than men, suggesting that sex differences in intramyocellular palmitate trafficking may occur under hyperinsulinemic conditions. We conclude that plasma FFA trafficking into imTG during hyperinsulinemia is markedly suppressed, and these newly incorporated FFA fatty acids do not readily enter the LCAC preoxidative pools. Hyperinsulinemia does not seem to inhibit the entry of fatty acids from imTG pools that were labeled under fasting conditions, possibly reflecting the presence of two distinct imTG pools that are differentially regulated by insulin.

Hepatolithiasis (Intrahepatic Stone) During Octreotide Therapy for Acromegaly: A Case Report

We report a case of hepatolithiasis (intrahepatic stone) complicated by gram-negative sepsis in a 37 year old male with acromegaly being treated with octreotide. As a child, he had suffered a traumatic injury to his liver requiring the surgical repair of a laceration. This is the first reported case of hepatolithiasis during octreotide therapy. Gallstones and bile sludge are common side effects of octreotide therapy but rarely become symptomatic or require treatment. Hepatolithiasis is uncommon in western countries but is quite prevalent in East Asia and is often associated with a predisposing condition that causes intrahepatic bile stasis (eg. bile duct stricture). In addition to its known effect on gallbladder stasis, octreotide alters bile acid composition and may thus hasten intrahepatic sludge and stone formation. Extra caution should be taken in using octreotide or its long-acting analog in patients otherwise predisposed to intrahepatic bile stasis.

Transient Hypothyroidism After Radioiodine for Graves’ Disease: Challenges in Interpreting Thyroid Function Tests

Graves’ disease is the most common cause of hyperthyroidism and is often managed with radioactive iodine (RAI) therapy. With current dosing schemes, the vast majority of patients develop permanent post-RAI hypothyroidism and are placed on life-long levothyroxine therapy. This hypothyroidism typically occurs within the first 3 to 6 months after RAI therapy is administered. Indeed, patients are typically told to expect life-long thyroid hormone replacement therapy to be required within this timeframe and many providers expect this post-RAI hypothyroidism to be complete and permanent. There is, however, a small subset of patients in whom a transient post-RAI hypothyroidism develops which, initially, presents exactly as the typical permanent hypothyroidism. In some cases the transient hypothyroidism leads to a period of euthyroidism of variable duration eventually progressing to permanent hypothyroidism. In others, persistent hyperthyroidism requires a second dose of RAI. Failure to appreciate and recognize the possibility of transient post-RAI hypothyroidism can delay optimal and appropriate treatment of the patient. We herein describe five cases of transient post-RAI hypothyroidism which highlight this unusual sequence of events. Increased awareness of this possible outcome after RAI for Graves’ disease will help in the timely management of patients.