Change of maternal thyroid function in twin-twin transfusion syndrome

Abstract

HUMAN CHORIONIC GONADOTROPIN (hCG) is part of the family of glycoprotein hormones, which have a common alpha-subunit and a unique beta-subunit. This family includes thyroid stimulating hormone (TSH). As a result, hCG has weak thyroid-stimulating activity [1]. In normal pregnancy, serum hCG concentrations rise soon after implantation and peak at 10 to 12 weeks of gestation, after which they decline. During the period of highest serum hCG concentrations, serum free triiodothyronine (fT3) and free thyroxine (fT4) concentrations increase, usually within the normal range, and serum TSH concentrations are correspondingly reduced. Transient subclinical hyperthyroidism occurs in 10% to 20% of normal pregnant women during the period of highest serum hCG concentrations; these women do not require treatment [2].Change of maternal thyroid function in twin-twin transfusion syndrome Masachi Hanaoka 1), 2) , Naoko Arata 2) and Haruhiko Sago Abstract. Human chorionic gonadotropin (hCG) has weak thyroid-stimulating activity because of its homology with thyroid stimulating hormone (TSH). In twin-twin transfusion syndrome (TTTS), which is a severe complication of monochorionic twin pregnancies, a close association between maternal serum hCG concentration and TTTS has been reported. And, TTTS can be treated by fetoscopic laser coagulation of the communicating vessels. To clarify the relationship between maternal serum hCG and maternal thyroid function in TTTS, the present study investigated the change in thyroid hormone and hCG levels after laser therapy. The protocol included collection of serial maternal blood samples in TTTS before laser therapy, and at two and four weeks after laser therapy. For 131 cases of TTTS, the following parameters were determined at each point: hCG, TSH, free triiodothyronine (fT3), and free thyroxine (fT4). The multiple of the median (MoM) of pre-operative hCG concentration in TTTS was 5.39 MoM (interquartile range, 2.83 -8.64). There was a moderate positive correlation between hCG and fT3 in TTTS pre-operatively (R = 0.22, P = 0.030). fT4 was also positively correlated with hCG (R = 0.33, P < 0.001). Some cases showed very high concentration in fT3. When laser therapy for TTTS was effective, the hCG concentration significantly decreased, and fT3 and fT4 decreased progressively in concert with the decrease in hCG. The relationship between hCG and thyroid function in TTTS supports the finding of TTTS as a novel etiology of hCG-mediated hyperthyroidism during pregnancy.Key words: Pregnancy, Human chorionic gonadotropin (hCG), Twin-twin transfusion syndrome (TTTS), Hyperthyroidism, Laser thearpyTwin-twin transfusion syndrome (TTTS) accounts for approximately 10% of monochorionic twin pregnancies. If left untreated, TTTS is associated with a high fetal morbidity and mortality rate [3]. A net transfusion of blood flow from one fetus (donor twin) to the other (recipient twin) via placental vascular anastomoses has been proposed as the major etiology of TTTS [4,5]. The donor twin becomes hypovolemic and oli...

Relapse of Human Chorionic Gonadotropin-Induced Hyperthyroidism and Severe Hyperemesis Gravidarum Secondary to Twin-Twin Transfusion Syndrome, With Rapid Recovery Following Fetoscopic Laser Coagulation: Case Report

“…In twin pregnancies, the overall kinetic pattern of maternal hCG remains unchanged, with a peak at 10-12 WG, followed by a sustained decrease until 20 WG, and then a stabilization during the second half of pregnancy (7). In this patient, the substantial sustained increase of hCG serum level up to 250000 IU/l at 14-17 WG was apparently related to TTTS (8,9), and it is likely to have been the cause of the subsequent HG worsening. TTTS is a severe complication of MC twin pregnancies occurring in nearly 10% of cases.…”

“…Nearly half of the patients had fT3 levels above the upper limit of the normal range. Even though fT3 levels were above the upper limit of the reference range in nearly 50% of women, clinical features were not described in the subgroup of women presenting with biochemically overt hyperthyroidism (9). In most cases, both fT4 and fT3 levels decreased concurrently with the decrease of hCG levels at 2 and 4 weeks after successful FLC (9).…”

“…Even though fT3 levels were above the upper limit of the reference range in nearly 50% of women, clinical features were not described in the subgroup of women presenting with biochemically overt hyperthyroidism (9). In most cases, both fT4 and fT3 levels decreased concurrently with the decrease of hCG levels at 2 and 4 weeks after successful FLC (9). The same pattern was also observed in the present patient; clinical symptoms of thyrotoxicosis were mild, and supportive therapy, such as betablockers, was not needed.…”

“…TTTS is associated with a significant increase of maternal hCG levels as compared to uncomplicated twin pregnancies in the mid-gestational period (8). In 131 pregnant women diagnosed with TTTS, median concentration of serum hCG between 16-26 WG was 96952 IU/l (interquartile range, 50964-155472), which was 5.4 times the median value in singleton pregnancies (9). Only 4 patients (out of 131, 3%) had hCG levels above 250000 IU/l, as observed in our case.…”

“…The limited literature (one published study available) on maternal thyroid function in the setting of TTTS suggests that TTTS could be considered a cause of hCG-induced maternal hyperthyroidism (9). However, to the best of our knowledge, there are no data describing the clinical symptoms and outcomes in women presenting altered thyroid function tests associated with TTTS.…”