Following the partial revision of the enforcement regulations of the School Health and Safety Act, school health checkups incorporated growth evaluation of schoolchildren in April 2016 using growth ...charts. We report cases of congenital central hypothyroidism (C-CH) in siblings with a novel nonsense variant in the immunoglobulin superfamily member 1 gene (IGSF1); their diagnoses were prompted by school health checkups. School checkups revealed that the older brother was overweight and had a reduced growth rate at the age of 11 yr, whereas the younger brother was overweight and had short stature at the age of 8 yr. They were diagnosed with C-CH because of normal thyroid-stimulating hormone (TSH) levels despite a low free thyroxine level and low TSH response in the thyrotropin-releasing hormone stress test. Only the older brother had prolactin deficiency and testicular growth without elevated testosterone levels. The siblings harbored a novel nonsense variant in exon 16 of IGSF1 (NM_001555.5: c.3056G>A: p.Trp1019Ter) and were diagnosed with IGSF1 deficiency. In Japan, C-CH may be overlooked because TSH-based newborn screening alone is usually performed for patients with congenital hypothyroidism. The implementation of growth monitoring using growth charts in school health checkups may prompt new C-CH diagnoses.
The hypothalamus-pituitary-thyroid axis is one of several hormone regulatory systems from the hypothalamus to the pituitary and ultimately to the peripheral target organs. The hypothalamus and the ...pituitary gland are in close anatomical proximity at the base of the brain and extended through the pituitary stalk to the sella turcica. The pituitary stalk allows passage of stimulatory and inhibitory hormones and other signal molecules. The target organs are placed in the periphery and function through stimulation/inhibition by the circulating pituitary hormones. The several hypothalamus-pituitary-target organ axis systems interact in very sophisticated and complicated ways and for many of them the interactive and integrated mechanisms are still not quite clear. The diagnosis of central hypothyroidism is complicated by itself but challenged further by concomitant affection of other hypothalamus-pituitary-hormone axes, the dysfunction of which influences the diagnosis of central hypothyroidism. Treatment of both the central hypothyroidism and the other hypothalamus-pituitary axes also influence the function of the others by complex mechanisms involving both central and peripheral mechanisms. Clinicians managing patients with neuroendocrine disorders should become aware of the strong integrative influence from each hypothalamus-pituitary-hormone axis on the physiology and pathophysiology of central hypothyroidism. As an aid in this direction the present review summarizes and highlights the importance of the hypothalamus-pituitary-thyroid axis, pitfalls in diagnosing central hypothyroidism, diagnosing/testing central hypothyroidism in relation to panhypopituitarism, pointing at interactions of the thyroid function with other pituitary hormones, as well as local hypothalamic neurotransmitters and gut-brain hormones. Furthermore, the treatment effect of each axis on the regulation of the others is described. Finally, these complicating aspects require stringent diagnostic testing, particularly in clinical settings with lower or at least altered à priori likelihood of hypopituitarism than in former obvious clinical patient presentations.
•The diagnosis of central hypothyroidism is mostly based on finding of a low/low normal free T4 estimate combined with an inappropriately low/normal serum TSH concentration.•In complicated cases such as suspicion of non-thyroidal illness or interfering factors, access to more elaborate laboratory measurements i.e. total T4, T3, a T4 or T3 uptake test and rT3 should be available to ensure a correct diagnosis.•Other hypothalamus-pituitary-hormone axes are also often affected in central hypothyroidism, depending on the underlying diagnosis.•The diagnosis of central hypothyroidism is affected by dysfunction from and interaction with the other axes.•Hypothalamus-pituitary-thyroid function is highly dependent on a variety of local hypothalamic neurotransmitters and gut-brain hormones.•Treatment of the central hypothyroidism and the other hypothalamus-pituitary axes influence each other by complex mechanisms.•Managing neuroendocrine disorders requires knowledge of the interactions between the hypothalamus-pituitary-hormones axes.
Objectives: Central hypothyroidism (CeH) is a rare form of hypothyroidism characterized by insufficient thyroid stimulation due to disturbed pituitary and/or hypothalamic functioning. Due to its ...origin and the whole clinical context, CeH represents a challenging condition in clinical practice as it is characterized by suboptimal accuracy of clinical and biochemical parameters for diagnosis and management. Since no expert consensus or guidance for this condition is currently available, a task force of experts received the commitment from the European Thyroid Association (ETA) to prepare this document based on the principles of clinical evidence. Study Design: The task force started to work in February 2017 and after a careful selection of appropriate references (cohort studies, case reports, expert opinions), a preliminary presentation and live discussion during the 2017 ETA meeting, and several revision rounds, has prepared a list of recommendations to support the diagnosis and management of patients with CeH. Results: Due to the particular challenges of this rare condition in the different ages, the target users of this guidance are pediatric and adult endocrinologists. Experts agreed on the need to recognize and treat overt CeH at all ages, whereas treatment of milder forms may be dispensable in the elderly (> 75 years). Conclusions: Despite the lack of randomized controlled clinical trials, the experts provide 34 recommendations supported by variable levels of strength that should improve the quality of life of the affected patients and reduce the metabolic and hormonal consequences of inadequate management.
Neonatal hyperthyroidism mainly occurring in the children born to mothers with Graves' disease (GD). The influence of maternal GD on the newborn's thyroid function includes not only hyperthyroidism, ...but also various forms of hypothyroidism. Maternally transferred thyrotropin receptor antibodies (TRAb), the antithyroid drug (ATD) administration during pregnancy and previous definitive treatment of GD (radioactive iodine therapy or thyroidectomy) in the mother impact the function of the fetal/neonatal thyroid. Some newborns born to mothers with GD may present central hypothyroidism (CeH) due to impaired regulation of the fetal hypothalamic-pituitary-thyroid axis. The aim of this study was to evaluate different types of thyroid dysfunction in babies with neonatal hyperthyroidism.
Medical records of 14 infants with neonatal hyperthyroidism (13 born to mothers with GD, and one born to mother with Hashimoto thyroiditis) were analyzed.
Transient hyperthyroidism was the main thyroid dysfunction in our study group. Overt hyperthyroidism with highly increased TRAb levels (mean 13.0 ± 7.0 IU/L) was diagnosed in 6 (43%) neonates. Another 6 (43%) babies presented hyperthyroidism with slightly increased fT4 and/or fT3 levels and TSH levels in the lower limit of the normal range coinciding with positive TRAb levels (mean 3.8 ± 1.6 IU/L). Normal thyroid hormone levels with TSH levels below the lower limit of the range were observed in 2 (14%) neonates. Four babies in the study group (28.5%) required further levothyroxine (L-T4) supplementation due to CeH or, in one case, due to primary hypothyroidism.
Our study highlights the need for prolonged monitoring of thyroid function in children born to mothers with GD. Diagnosis of CeH could be delayed due to its masking by transient hyperthyroidism. Prolonged thyroid-stimulating hormone suppression after TRAb elimination should be considered as a signal announcing CeH.
Background
Thyroid testing strategies vary across laboratories. First‐line combined thyroid stimulating hormone (TSH) and freeT4 (FT4) have historically been preferred by many laboratories as this ...detects individuals with undiagnosed central hypothyroidism who can be missed with a first‐line TSH‐only strategy. However, an up‐to‐date evaluation of the utility of this approach is lacking.
Objectives
We investigated the clinical utility of first‐line TSH and FT4 in the detection of central hypothyroidism in current day practice.
Design, Patients, and Measurements
The All‐Wales laboratory information system was queried to identify thyroid function tests in patients aged ≥16 years with decreased FT4 and inappropriate TSH (low‐FT4). The 1‐year incidence of low‐FT4 was determined using mid‐year population data. Clinical information of patients with low‐FT4 was reviewed to determine causes of low‐FT4 and the incidence of central hypothyroidism.
Results
The incidence of low‐FT4 varied according to FT4 assay method (range: 98–301 cases/100,000 population/year). Fifteen new cases of central hypothyroidism were detected in two health boards, equivalent to 2 cases/100,000 population/year. Positive predictive value of low‐FT4 for central hypothyroidism was 2%–4%. In a cross‐section of primary care patients, low‐FT4 was detected in 0.5% of all thyroid tests with assay‐related differences in detection rates.
Conclusions
Although low‐FT4 is a common laboratory finding, the incidence of central hypothyroidism remains rare. With the currently increased rates of thyroid testing and increased use of medications that decrease FT4, low‐FT4 has a much lower predictive value for central hypothyroidism than previously reported. Thyroid screening strategies will need to balance the yield from first line TSH and FT4 testing with the cost of investigating individuals with non‐pathological laboratory abnormalities.
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