Reprod Nutr Dev. ;29(4) Thyroid hormone and growth: relationships with growth hormone effects and regulation. Cabello G(1), Wrutniak C. Acta Endocrinol Suppl (Copenh). ; The interrelationships of thyroid and growth hormones: effect of growth hormone releasing hormone in hypo-. concentration of thyroid hormone subtypes following growth hormone relationship between serum TSH and free T4 – the TSH index – in.
Eleven patients had idiopathic GH deficiency. Four patients had organic GH deficiency, three had received central nervous system radiation, and two had central diabetes insipidus treated with desmopressin acetate Rorer Pharmaceuticals, Fort Washington, PA.
No other endocrine therapy was given during the year of the study. This study was approved by the human research review committee of the Medical College of Wisconsin and the human rights review board of Childrens Hospital of Wisconsin. Written informed consent was obtained from all families.
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The FT4I was calculated as the product of T4 and the normalized T4 resin uptake, with a normal range of 80— TSH was measured by an immunoradiometric assay Serono Laboratorieswith a normal range of 0. The TSH area under the curve was calculated by the trapezoidal rule.
Each run had its own standard curve, internal control, and duplication. The interassay coefficient of variation for T4 was 3.
Fasting cholesterol was obtained at baseline and after 6 and 12 months of therapy. At each clinic visit, attention was given to signs or symptoms of hypothyroidism, such as constipation, fatigue, cold intolerance, skin or hair changes, delayed Achilles reflex relaxation phase, or poor response to GH therapy.
Statistical analysis was performed with SigmaStat for Windows version 2. Data were analyzed for normality Kolmogorov-Smirnov test and equal variance Levine Median ; nonparametric testing was performed whenever data did not meet both these criteria. As there were no significant differences in thyroid data between the daily and the thrice weekly groups, all reported analyses were for the combined group.
Exploratory analyses with Pearson product-moment correlations were performed between clinical variables age; baseline and year-end height or height age; baseline and year-end weight, ponderal index; baseline and year-end growth velocity; and baseline and year-end height and velocity sd scorebetween lab variables all thyroid values; baseline and year-end IGF-Iand between both clinical and lab variables to detect possible predictive variables for the first year growth velocity response Vel-1 or Vel-1 sd score.
Both best subsets for optimum Cp and adjusted r2 and forward stepwise regression analyses were then used to confirm significant predictive variables with minimal multicollinearity for final models of prediction of first year velocity Results The daily group weighed less at baseline For all other auxological or biochemical parameters, there were no significant differences between the daily and thrice weekly groups.
Thyroid hormone and growth: relationships with growth hormone effects and regulation.
Conclusions The incidence of HypoT during the initial phase of GH treatment in children with GHD and the negative effect of even transient thyroid hormone deficiency on the growth rate should be taken into account. The main goal of the treatment is to increase patients' height velocity HV and to improve the attained final height FH. Besides, either normal thyroid hormone secretion or appropriate substitution of L-thyroxine L-T4 is necessary for the optimal effect of both endogenous GH and rhGH substitution on the growth rate.
The relationships between GH secretion and thyroid function, as well as the effects of rhGH administration on thyroid hormone levels have been the subject of numerous studies. The data of Cacciari et al. Moreover, in some of those patients before rhGH administration, serum T3 levels were subnormal despite T4 substitution and normalised during the therapy.
As it was shown that rhGH administration might induce a fall in serum T4, it seemed probable that GHD could mask secondary hypothyroidism in some patients with hypopituitarism. Recently, Agha et al. Similar were the observations of Losa et al. First reports, concerning the effects of rhGH therapy on thyroid hormone levels in children also confirmed an increase of extrathyroidal conversion of T4 to T3 during the therapy [ 6 ].
Conversely than described for adults [ 5 ], as early as inLaurberg et al. Up to now, several interesting studies have been published on long-term effects of rhGH replacement therapy on thyroid function, both in adults [ 8 - 10 ] and in children [ 11 - 18 ]. The aim of current study was to evaluate the effect of rhGH substitution on TSH and FT4 serum concentrations in children with GHD during the 1st year of therapy, as well as to assess potential indications to thyroid hormone supplementation in them.
Patients and methods The retrospective analysis involved the data of 75 children 59 boys, 16 girls with GHD, who were qualified to rhGH therapy. At therapy onset, the patients' height was below the 3rd centile, according to Polish reference charts [ 19 ], HV was slow below Thyroid function was normal in most of children 67 cases.
In the remaining 8 patients, L-T4 supplementation had been administered, due to either hyperthyrotropinemia or relatively low normal but close to the lower limit of reference range FT4 concentration and pharmacological euthyrodism was then confirmed. In most of the children, IGF-I concentration was either decreased or close to lower limit of normal range. In all the patients, nocturnal GH secretion was assessed during 3 hours after falling asleep 5 samples every 30 minutes from the 60th to the th minute and 2 stimulating tests were performed with clonidine 0.
Neurosecretory dysfunction NSD was diagnosed in children with normal results of stimulating tests but decreased nocturnal GH secretion that observation had to be confirmed by documenting decreased GH secretion in prolonged, 6-hour nocturnal profile. In children with decreased IGF-I secretion and normal GH peak both in nocturnal profile and after pharmacological stimulationIGF-I generation test was performed after exclusion of other causes of IGF-I deficiency, not related to GH secretion disorders and GH action like malabsorption syndromes, liver diseases, malnutrition, other severe chronic diseases.