Water metabolism disturbances at different stages of primary thyroid failure

Abstract

The aim of the present study was to study salt and water metabolism in thyroid deficiency.We performed an oral water loading test (OWL) and a hypertonic 5% saline infusion test (HSI) in 16 patients with overt primary hypothyroidism before replacement treatment (PRE group) and after, in eight patients with subclinical hypothyroidism (SUB group) and in 16 normal individuals (CG group).In the PRE group, a lower free water clearance was detected in the OWL (P<0·022), with lower plasma osmolality (OWL: P<0·005; HSI: P<0·001) and arginine vasopressin (AVP) (OWL: P<0·001; HSI: P<0·001) than the CG group, across both tests; they normalized with the replacement treatment. The same plasma abnormalities were detected in the SUB group with the HSI. Although the AVP and thirst thresholds did not differ between the groups, the lag between them was lower in the PRE (4·1 3·2 mOsm/kg) and SUB group (2·6 2·1 mOsm/ kg) than in the CG group (13·3 9·2 mOsm/kg) (P<0·05). There were no differences in atrial natriuretic hormone (ANH), plasma renin activity (PRA) and plasma aldosterone among the groups.These results indicate that plasma hypo-osmolality and low levels of AVP are present in primary hypothyroidism, and indeed are already present in the subclinical phase of the disease. An overlap between the thresholds of thirst and AVP seem to play a role in these abnormalities, but ANH, PRA and plasma aldosterone do not appear to contribute.

Sex-specific phenotypes of hyperthyroidism and hypothyroidism in mice

“…However, decreased water consumption did not affect the success of LoI/MMI/ClO 4 − treatment as TT 4 serum concentrations were below limit of detection and serum TSH was highly elevated to comparable values for both sexes. The manipulation of TH status might also affect hormonal regulation of fluid intake, water and salt homeostasis, an observation compatible with altered water metabolism in hypothyroid patients [21, 22] and increased hypothalamic vasoactive intestinal polypeptide-immunoreactive neuron expression in hypothyroid rats [23]. For other phenotypic traits related to the manipulation of TH concentration, sex-specific differences persisted (e.g., body temperature in hyper- and hypothyroidism), were exaggerated (e.g., food intake in hyperthyroidism) or disappeared (e.g., BW change in hypothyroidism).…”

Short-Term Weight Changes in Treated Primary Hypothyroid Subjects

“…Primary hypothyroidism is usually associated with weight gain resulting from a reduction of basal metabolic rate (BMR), decreasing level of spontaneous physical activity level due to alteration of skeletal muscle metabolism and function, psychomotor slowing and impaired cardiac output, and accumulation of water-binding glycosaminoglycans which led to the term myxedema [8]. Reduced capacity of renal free-water excretion, increased antidiuretic hormone level, and increased protein extravasation to a decreased lymphatic drainage have also been described which also contribute to weight gain in hypothyroidism [9][10][11]. Treatment of hypothyroidism has been found to be associated with decreased body weight attributable to a decrease in lean mass because the total fat mass was largely unchanged and it is hypothesized that the weight loss often observed during such treatment is predominantly due to loss of excess body water accumulated during the state of myxedema [8].…”

Hipotiroidizmde Ödem Mekanizmaları

“…Hipotirodi olgularında tiroid hormon replasmanı tedavisi sonrasında renin aktivitesi 8 kat, aldosteron düzeyi ise 2,5 kat artmıştır. Hipotiroidizmde renin-aldosteron mekanizmasının bozulmadığını bildiren yayınlar vardır (5,17).…”

“…Hipotiroidizmde kardiyak debinin düşmesinin karotis sinüsdeki baroreseptörleri stimüle ederek ADH salınıma neden olduğu bildirilmiştir (12). Ancak hipotiroidizmde ADH düzeyinin normal veya düşük bulunduğu araştırmalar da vardır (5). Tiroid hormonlarının (T3,T4) santral bir mekanizma ile ADH salınımını baskıladığı düşünülmektedir (13).…”