Inherited X chromosome linked thyroxine-binding globulin (TBG) deficiency in a homozygous female.

Of the 37 families with TBG deficiency so far described, 31 were shown to be compatible with X chromosome linked mode of inheritance, and in 5 of the remaining 6 this mode of transmission was suspected. Difficulties in proving X chromosome linkage in some families was usually due to the inability to identify the heterozygous female carriers when affected males were only partially TBG deficient. This work describes a new family with inherited TBG deficiency which on first glance showed inconsistencies with X chromosome linked inheritance. More specifically, there was an apparent male to male transmission of the trait and the presentation in one female of low TBG, phenotypically indistinguishable from the affected males. Studies on three generations identified TBG deficiency on both the maternal and paternal branches of the family. We were thus able to prove that the affected male inherited the trait from his heterozygous mother, rather than from his father, and that the female with more severe TBG deficiency was homozygous for the trait through acquisition of a defective X chromosome from both mother and father. The latter explained her phenotype presentation indistinguishable from that in affected hemizygous males. Thus, unless proven otherwise, all inherited TBG abnormalities in man appear to be X chromosome linked. Because of the relatively common prevalence of inherited TBG defects, marriages among such individuals are expected to give rise to a progeny with an unusual phenotypic presentation. All members of the family were clinically euthyroid and affected members showed a normal TSH response to TRH.

Age- and sex-related variations of serum thyroxine binding globulin.

Measurements of serum thyroxine binding globulin (TBG) by a ligand partitioning sandwich assay were performed in 173 healthy subjects between three months and 92 yr of age. Significant sex-related differences were observed in subjects aged 21 to 50 yr. In males, serum TBG declined progressively reaching a nadir in the fourth decade and then increased with advancing age. In contrast, no significant age-related variation was observed in females.

A pregnancy in an acromegalic woman during bromocriptine treatment: effects on growth hormone and prolactin in the maternal, fetal, and amniotic compartments.

An unexpected 20-week-old pregnancy was found in a young acromegalic who had been treated with 10 mg bromocriptine/day for 10 months. The drug was continued throughout the period of gestation. No growth of the pituitary adenoma was noticed. The intrauterine development of the fetus was normal. Bromocriptine therapy had no discernible effect on the expected patterns of secretion of placental hormones, but inhibited completely the increase of PRL in the serum of the mother. Maternal plasma GH concentrations were very high in spite of the treatment and progressively declined after delivery. The plasma GH level was normal in the child, but PRL was very low at birth and increased in the following days. The expected high PRL concentration was found in the amniotic fluid. This case study suggests that bromocriptine crosses the human placenta and affects the fetal pituitary, maternal GH does not influence fetal or amniotic GH, and amniotic fluid PRL correlates poorly with either maternal or fetal blood levels and is not affected by bromocriptine.