Hypothyroidism
	Stenlöf et al., Göteborg, Sweden, studied body composition in 10 hypothyroid subjects (age 18-64 years) before and after 3 months of T4 treatment. Between these time points no significant changes were seen in body weight, lean body mass or body fat as measured with dual-energy X-ray absorptiometry (DEXA). However, using CT scanning, subcutaneous fat increased (p < 0.01) and muscle tissue decreased (p < 0.05). No change was seen in visceral adipose tissue. A negative relationship at 3 months was found between increase in subcutaneous adipose tissue and the FT3/FT4 ratio (r -0.78, p < 0.01). Brenta et al., Buenos Aires, Argentina, studied isoforms of sex hormone binding-globulin (SHBG) in 6 hypothyroid women and results were compared with 6 controls. The reason for this study was that, although in hyperthyroidism SHBG serum concentrations are increased, values in hypothyroidism are unexpectedly frequently normal. The essence of their findings is that there is a change in the three isoforms of SHBG in hypothyroid women, in that the isoforms have a higher sialic content than in controls. This phenomenon, according to the authors, could explain the mostly normal SHBG values in hypothyroidism. (Comment: the sialic moiety bound to SHBH increases its half-life in the circulation, which results in an increased concentration. This situation is comparable to the serum TBG concentration in pregnancy and during oestrogen usage, that is increased as well due to its increased sialic content.) Meier et al., Basel, Switzerland, related markers of hypothyroidism i.e., clinical score, ankle reflex time, serum creatine kinase and total and LDL cholesterol, in 192 patients with subclinical hypothyroidism (age 54.3 ± 9 years, TSH 13.5 ± 0.9 mU/l) and 58 patients with overt hypothyroidism (56.3 ± 5 years, TSH 50.5 ± 3.4 mU/l). They found in subclinical hypothyroidism a weak but significant relationship between markers and TSH and FT4. In overt hypothyroidism no correlation was found between markers and serum TSH, but a stronger correlation with FT4. The authors conclude that the absent correlation between TSH and markers of hypothyroidism in overt hypothyroidism, is due to the fact that in severe hypothyroidism pituitary TSH secretion is under maximal stimulation and does not increase further when hypothyroidism progresses. (Comment: It has been shown that both in rats and in humans there is even a drop in serum TSH in most severe hypothyroidism due to inhibition of protein synthesis as reflected also by a decrease in growth hormone production. This fact may additionally explain the here reported absence of correlation.) Iervasi et al., Pisa, Italy, studied neuroendocrine control of blood pressure in 13 subjects on suppressive T4 therapy after total thyroidectomy + I-131 ablation for thyroid carcinoma, 6 weeks after T4 withdrawal (mean TSH 65mU/L) and subsequently 2 months after T4 suppressive therapy had been resumed (mean TSH 0.18mU/L). At these time points, diastolic blood pressure decreased significantly from 84 ± 7 to 76 ± 8 mmHg (p < 0.05), while plasma noradrenaline and aldosterone also decreased significantly. Systolic blood pressure values remained unaltered as did plasma renin activity. Significant negative correlations were present between FT3 and noradrenaline levels and diastolic blood pressure. The authors conclude that the increase in diastolic blood pressure in severe hypothyroidism is associated with sympathetic activation while the reversible increase in aldosterone levels suggest a direct effect of thyroid hormones on its production and/or degradation.