Transient secondary hypothyroidism and thyroxine binding globulin deficiency in leukemic children during polychemotherapy: an effect of L-asparaginase

Thyroid dysfunction during treatment with systemic antineoplastic therapy for childhood cancer: A systematic review

Thyroid dysfunction is known to occur following radiotherapy or chemotherapy for childhood cancer. Thyroid dysfunction during treatment for childhood cancer has, however, not been studied extensively, although thyroid hormones are of utmost importance during childhood. This information is needed to develop adequate screening protocols and may be of special importance with upcoming drugs, such as checkpoint inhibitors, which are highly associated with thyroid dysfunction in adults. In this systematic review we have evaluated the occurrence and risk factors for thyroid dysfunction in children during treatment with systemic antineoplastic drugs, up to three months after the end of therapy. Two review authors independently performed the study selection, data extraction and risk of bias assessment of included studies. After an extensive search (January 2021), in total six heterogeneous articles were included, reporting on 91 childhood cancer patients with a thyroid function test during treatment with systemic antineoplastic therapy for childhood cancer. All studies had risk of bias issues. Primary hypothyroidism was found in 18% of children treated with high dose interferon-α (HDI-α) and in 0-10% after tyrosine kinase inhibitors (TKIs). Transient euthyroid sick syndrome (ESS) was common (in 42-100%) during treatment with systematic multi-agent chemotherapy. Only one study addressed possible risk factors, showing different types of treatment to increase the risk. However, the exact prevalence, risk factors and clinical consequences of thyroid dysfunction remain unclear. Prospective high-quality studies including large study samples are needed to longitudinally assess the prevalence, risk factors and possible consequences of thyroid dysfunction during childhood cancer treatment.

Thyroid Profile in the First Three Months after Starting Treatment in Children with Newly Diagnosed Cancer

BACKGROUND

Thyroid hormone anomalies during childhood might affect neurological development, school performance and quality of life, as well as daily energy, growth, body mass index and bone development. Thyroid dysfunction (hypo- or hyperthyroidism) may occur during childhood cancer treatment, although its prevalence is unknown. The thyroid profile may also change as a form of adaptation during illness, which is called euthyroid sick syndrome (ESS). In children with central hypothyroidism, a decline in FT4 of >20% has been shown to be clinically relevant. We aimed to quantify the percentage, severity and risk factors of a changing thyroid profile in the first three months of childhood cancer treatment.

METHODS

In 284 children with newly diagnosed cancer, a prospective evaluation of the thyroid profile was performed at diagnosis and three months after starting treatment.

RESULTS

Subclinical hypothyroidism was found in 8.2% and 2.9% of children and subclinical hyperthyroidism in 3.6% and in 0.7% of children at diagnosis and after three months, respectively. ESS was present in 1.5% of children after three months. In 28% of children, FT4 concentration decreased by ≥20%.

CONCLUSIONS

Children with cancer are at low risk of developing hypo- or hyperthyroidism in the first three months after starting treatment but may develop a significant decline in FT4 concentrations. Future studies are needed to investigate the clinical consequences thereof.

Alteration of Thyroid Function in Indian HER 2-Negative Breast Cancer Patients Undergoing Chemotherapy

BACKGROUND

Thyroid hormones (TH) are regulated by the hypothalamic-pituitary axis, which plays an important role in cell growth, differentiation, development and other aspects of metabolism. It is believed that an active hypothalamic-pituitary axis increases the susceptibility of thyroid dysfunction during systemic chemotherapy. In order to investigate the relation between thyroid function and chemotherapy the present study was designed to investigate TH in breast cancer patients receiving at least three cycles of chemotherapy. The levels of TH were measured at the baseline and before each cycle of chemotherapy.

MATERIALS AND METHODS

Blood samples for estimation of TH levels were collected from 80 (pre-menopausal-40; post-menopausal-40) breast cancer patients just before they were undergoing--1st, 2nd, 3rd and 4th cycle of chemotherapy. The serum was separated and T3, T4 and TSH levels were determined by chemiluminescence method.

RESULTS

T3 and T4 were found significantly decreased and TSH was found significantly increased after 1st (p<0.001), 2nd (p<0.0001) and 3rd cycle of chemotherapy (p<0.0001). The variation of T3 levels (decreased) and TSH levels (increased) was found more in post-menopausal (p<0.0001) women then in pre-menopausal women after 3rd cycle of chemotherapy as compared to baseline (p<0.001).

CONCLUSIONS

TH were remarkably altered after each cycle of chemotherapy leading to decline in thyroid function of breast cancer patients. Further, the results also indicated that post- menopausal women were more prone towards decline in thyroid function then pre-menopausal women. The present study proposes the monitoring of TH after each cycle of chemotherapy in breast cancer patients.

Thyroid dysfunction as an unintended side effect of anticancer drugs

BACKGROUND

Several of the currently used anticancer drugs may variably affect thyroid function, with impairment ranging from modified total but not free concentration of thyroid hormones to overt thyroid disease.

SUMMARY

Cytotoxic agents seem to alter thyroid function in a relatively small proportion of adult patients. Anticancer hormone drugs may mainly alter serum levels of thyroid hormone-binding proteins without clinically relevant thyroid dysfunction. Old immunomodulating drugs, such as interferon-α and interleukin-2, are known to induce variably high incidence of autoimmune thyroid dysfunction. Newer immune checkpoint inhibitors, such as anti-CTLA4 monoclonal antibodies, are responsible for a relatively low incidence of thyroiditis and may induce secondary hypothyroidism resulting from hypophysitis. Central hypothyroidism is a well-recognized side effect of bexarotene. Despite their inherent selectivity, tyrosine kinase inhibitors may cause high rates of thyroid dysfunction. Notably, thyroid toxicity seems to be restricted to tyrosine kinase inhibitors targeting key kinase-receptors in angiogenic pathways, but not other kinase-receptors (e.g., epidermal growth factor receptors family or c-KIT). In addition, a number of these agents may also increase the levothyroxine requirement in thyroidectomized patients.

CONCLUSIONS

The pathophysiology of thyroid toxicity induced by many anticancer agents is not fully clarified and for others it remains speculative. Thyroid dysfunction induced by anticancer agents is generally manageable and dose reduction or discontinuation of these agents is not required. The prognostic relevance of thyroid autoimmunity, overt and subclinical hypothyroidism induced by anticancer drugs, the value of thyroid hormone replacement in individuals with abnormal thyrotropin following anticancer systemic therapy, and the correct timing of replacement therapy in cancer patients need to be defined more accurately in well-powered prospective clinical trials.

Effects of the antileukemic drug L-asparaginase on sex hormone-binding globulin: studies in vivo and in vitro

L-asparaginase, an antineoplastic drug used in the treatment of acute lymphoblastic leukemia (ALL), has been previously shown to inhibit the hepatic synthesis of thyroxine-binding globulin (TBG). In two children treated by this drug for ALL, a dramatic decrease in serum sex hormone-binding globulin (SHBG) concentrations was also observed. Serum SHBG levels were still below normal 10 days after L-asparaginase withdrawal. To ascertain whether this reduction was due to the inhibition of SHBG synthesis, SHBG was measured by an immunoradiometric assay (IRMA) in the medium from human hepatoblastoma-derived cells, Hep G2 cells, grown in the absence or presence of graded amounts of the drug from 0.1 nM to 0.1 mM. The results showed a dose-dependent inhibition of SHBG synthesis, with a 50% reduction of SHBG in the medium, assayed by IRMA, using 250 nM L-asparaginase. Furthermore, a time-dependent inhibition was observed using a fixed concentration of the drug (50 nM) added for variable time intervals (1-4 days). These data suggest that the changes observed in vivo are likely due to the inhibitory effect exerted by the drug on SHBG synthesis. This action is not specific, but is part of a general effect at the hepatic level.

Sleep-related gonadotropin rhythms in children following treatment of acute leukemia: recovery of the hypothalamo-pituitary-gonadal axis after chemotherapy and CNS-irradiation

Twelve children (5 girls and 7 boys, between the ages of 6 and 20 years) in complete remission from previous ALL who had completed their entire anti-leukemic treatment program and who had been off all chemotherapy for at least one year, were included in a study of sleep-related prolactin and gonadotropin rhythms. All the patients had received prophylactic CNS-irradiation. The patients in early puberty showed a sleep-dependent FSH rhythm. Patients in middle-to-late puberty had sleep-related FSH and LH rhythms, and estradiol and testosterone plasma concentrations were normal for their pubertal stage, suggesting recovery of the hypothalamo-pituitary-gonadal feedback system. We conclude that the neuro-endocrine axis is not permanently injured by CNS-irradiation and anti-leukemic therapy.