Triceps brachii strength and regional body composition changes after detraining quantified by MRI.

PURPOSE: To determine the triceps brachii functional adaptation and regional body composition changes after 12 months of detraining. MATERIALS AND METHODS: Seventeen healthy young men (22.2 ± 1.0 y, body mass index 24.9 ± 3.1 kg/m(2) ) were put in the detraining regimen for 12 months after completing a 12-week exercise protocol on isoacceleration dynamometer (5 times a week, 5 daily series with 10 maximal elbow extensions, 1 min rest between sets). Triceps brachii muscle strength was measured by isoacceleration dynamometry, using identical protocol as during the training. Muscle volumes, subcutaneous adipose tissue (SCAT), and intermuscular adipose tissue (IMAT) at mid-humerus were assessed by using MRI. RESULTS: Long-term detraining resulted in the significant decrease of 17% and 19% in endurance strength and fatigue rate, respectively. Maximal muscle strength slightly changed, and its 4% decrease was not significant. Triceps brachii volumes of both arms returned to their pretraining values (475.7 ± 54.91 cm(3) for right arm, and 483.9 ± 77.5 cm(3) for left arm). IMAT depots in upper arm significantly increased by 14% after 12 months of detraining, when compared with baseline values (P < 0.05). CONCLUSION: Long-term detraining leads to triceps brachii adaptation with endurance strength decrease, volume return to its baseline values, and significant IMAT accumulation. IMAT values after 12 months of detraining exceed baseline, pretraining values, which is significant accumulation as a result of physiologically decreased muscle activity.

[Bone mineral density in patients on long-term therapy with levothyroxine]. / Mineralna gustoca kosti u bolesnica na dugotrajnoj terapiji levotiroksinom.

The aim of the study was to determine the influence of replacement and suppressive thyroxine therapy on bone mineral density (BMD). 30 postmenopausal women; 19 on replacement therapy (dose 1.22 +/- 0.35 micrograms/kg; duration 11.4 +/- 7.2 years) and 11 on suppressive therapy (dose 1.45 +/- 0.71 micrograms/kg; duration 9.5 +/- 7.2 years). Controls were 60 healthy women matched for age and menopausal status. BMD at the lumbar spine (L2-L4), femoral neck, Ward's triangle and trochanter was measured by dual-energy absorptiometry. Forearm BMD at distal site was measured by single-photon absorptiometry. Mean thyroid hormone values and TSH were within normal limits, although the patients on suppressive therapy had significantly higher T3 (p < 0.05) than the patients on replacement therapy. BMD on each site was significantly lower in the replacement treated group than in controls. BMD in patients on suppressive therapy was lower, but not significantly, compared to controls. Thyroxine therapy could have an adverse effect on BMD. The magnitude of bone loss depends on the serum level of thyroid hormones and on the functional state of thyroid hormone receptor in bone tissue, as well.

Effects of ritanserin, a novel serotonin-S2 receptor antagonist, on the secretion of pituitary hormones in normal humans.

The availability of a new potent and selective serotonin-S2 antagonist, ritanserin (RIT), encouraged us to further investigate the effect of serotonin on the basal secretion of anterior pituitary hormones in normal humans. Administered in a single 30-mg dose to group 1 consisting of 10 normal women, RIT failed to affect the baseline LH, FSH, GH or TSH levels. In group 2 consisting of 20 normal subjects (ten males and ten females), the same dose of RIT decreased in parallel both ACTH and cortisol levels but only at 180 min. Group 3 consisting of 8 normal men was studied on three separate occasions seven days apart: each subject received graded doses of 10 mg, 20 mg and 30 mg RIT. The mean baseline PRL concentration at 180 min as well as the net integrated area under the hormone curve (nAUC) decreased only after the highest dose, while the baseline cortisol concentrations at 180 min as well as the corresponding nAUC values displayed a clear dose-dependent response. The findings indicated the serotonin-S2 receptors to be only partially involved in the basal secretion of ACTH in normal humans.

Effects of ritanserin, a specific serotonin-S2 receptor antagonist, on the release of anterior pituitary hormones during insulin-induced hypoglycemia in normal humans.

The role of serotonin in the insulin hypoglycemia (IH) stimulated secretion of prolactin (PRL), growth hormone (GH), adrenocorticotropin (ACTH) and cortisol (F) was studied in a group of 12 normal subjects during the control period after placebo and a consecutive six-day treatment with 20 mg ritanserin (RIT) per day. RIT failed to affect the baseline levels of all the four hormones as well as the PRL response to IH (p > 0.5). The serum GH response to IH was moderately diminished after RIT, the reduction of integrated trapezoidal area under hormone curves (nAUC) being 50.7% +/- 6.9% (p < 0.005). Furthermore, RIT was found to slightly decrease the plasma ACTH response to IH, the reduction of nAUC being 36.3% +/- 2.6% (p < 0.005). Decrease in the corresponding plasma F response to IH was accompanied by 29.1% +/- 2.4% reduction of nAUC (p < 0.005). According to our results, serotonin-S2 receptors appeared to be moderately involved in IH-induced release of GH, but slightly in that of ACTH, leaving unaffected that of PRL.