Daylong pituitary hormones in morbid obesity: effects of bariatric surgery

Abstract

Moderate obesity is known to be associated with multiple endocrine abnormalities. Less information is available on the hormonal status of patients with morbid obesity and on the effects of major weight loss. We studied 16 severely obese (BMI 40.6-69.9 kg/m 2 ) nondiabetic patients and 7 nonobese (BMI range 24.6-27.7 kg/m 2 ), sex-and age-matched healthy volunteers. During 24 h in a metabolic ward, four meals were administered and hourly blood samples were drawn from a central venous catheter for the measurement of glucose, insulin, leptin, thyrotropic hormone (TSH), growth hormone (GH) and prolactin. Insulin sensitivity was measured by a euglycaemic hyperinsulinaemic clamp. Studies were repeated 6 months after biliopancreatic diversion, a mainly malabsorptive surgical approach, which caused an average weight loss of 35±4 kg (or 26 ± 2% of initial weight). Compared with controls, patients were hyperinsulinaemic (290 ± 31 vs 88 ± 4 pmol l À1 , P ¼ 0.0002), insulin resistant (23.5±2.8 vs 52.9±4.9 mmol min À1 kg FFM À1 , P ¼ 0.0006) and hyperleptinaemic (52.5±5.8 vs 10.9±3 ng ml À1 , P ¼ 0.0002). Plasma TSH levels were increased throughout the day-night cycle (averaging 2.02 ± 0.18 vs 1.09 ± 0.19 mU ml À1 of controls, P ¼ 0.01), whereas serum GH levels were suppressed (0.46±0.10 vs 3.01±1.15, P ¼ 0.002). Following surgery, the hyperinsulinaemia and insulin resistance were fully normalized; in concomitance with a major drop in leptin levels (to 14.4±2.7 ng ml À1 , P ¼ 0.02), TSH decreased and GH increased to near-normal levels. In the whole dataset, mean 24-h leptin levels were directly related to mean 24-h TSH levels after controlling for confounders this relationship was lost only after adjusting for fat mass. We conclude that in morbid obesity leptin is a determinant of changes in pituitary function.

A Morbid Obese Japanese Woman with a Body Mass Index of 83.2 kg/m²: Before and after Sleeve Gastrectomy

“…This may be one of the factors that she is maintaining her normal glycemia and lipid profiles despite her continued obesity. Though an increase in TSH levels has been reported in the morbidly obese (43), the levels of TSH, fT3 and fT4 in the present case were in normal range and did not change postoperatively.…”

“…Growth hormone (GH) secretion is influenced by body composition, and in patients with obesity, GH production peaks are few and suppressed (43)(44)(45). Also, it has been reported that GH is stimulated by ghrelin (46,47).…”

Expression of thyrotropin and thyroid hormone receptors in adipose tissue of patients with morbid obesity and/or type 2 diabetes: effects of weight loss

“…In morbidly obese patients with subclinical hypothyroidism, bariatric surgery led to changes in obesity-related adipokines believed to influence the synthesis and secretion of thyroid hormones. 9,19 However, in a recent study from our laboratory, 10 the direct relationship between 24-h mean concentrations of TSH and leptin in euthyroid obese patients was lost after adjusting for fat mass, suggesting that other mechanisms modulate TSH concentrations in morbidly obese patients. Another explanation is that the thyroid hormone profile of the obese individuals reflects pituitary resistance to thyroid hormones, with a variable degree of secondary impairment of thyroid hormone peripheral metabolism.…”

“…On the other hand, this study is one of the few investigations that have unequivocally shown that weight loss leads to a reduction in both TSH and FT 3 levels. 9,10,19,20 Several explanations have been proposed to account for the influence of obesity on thyroid hormones. One suggests that the increased TSH level could reflect pituitary adaptation to increased adiposity through adipokines.…”

“…5 More recent studies have confirmed that diurnal serum TSH levels are significantly increased, if still within the normal range, in obese individuals, and that major weight loss induces a sizeable reduction in TSH and thyroid hormone levels. [8][9][10] It is unknown whether TSH has a role in favoring fat deposition or, on the contrary, whether excessive accumulation of adipose tissue increases TSH secretion. Recent evidence in experimental animals and in humans has shown that adipocytes and preadipocytes possess TSH receptors (TSHRs), [11][12][13] and that TSH action induces the differentiation of preadipocytes into adipocytes, adipogenesis and, in children, lipolysis.…”