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An Ex vivo Culture System to Study Thyroid Development
08:33

An Ex vivo Culture System to Study Thyroid Development

Published on: June 6, 2014

A lack of thyroid hormones rather than excess thyrotropin causes abnormal skeletal development in hypothyroidism

J H Duncan Bassett1, Allan J Williams, Elaine Murphy

  • 1Molecular Endocrinology Group, Medical Research Council Clinical Sciences Centre, Hammersmith Hospital, Du Cane Road, London, United Kingdom.

Molecular Endocrinology (Baltimore, Md.)
|October 13, 2007
PubMed

Insights

Thyroid hormone (T3) action, not TSH, is crucial for bone health. Studies show congenital hypothyroidism in mice leads to bone defects regardless of TSH levels, confirming T3

Area of Science:

  • Endocrinology
  • Bone Biology
  • Skeletal Physiology

Background:

  • Recent research proposed TSH as a negative regulator of bone turnover, challenging the established role of thyroid hormone (T3) in skeletal responses to hypothalamic-pituitary-thyroid axis disruption.
  • This hypothesis fails to explain osteoporosis risk in Graves' disease, characterized by TSH receptor (TSHR)-stimulating antibodies.

Purpose of the Study:

  • To elucidate the distinct roles of T3 and TSH in bone metabolism.
  • To compare skeletal phenotypes in mouse models of congenital hypothyroidism with intact or disrupted T3-TSH relationships.

Main Methods:

  • Comparison of skeletal phenotypes in Pax8 null (high TSH, normal TSHR) and hyt/hyt (high TSH, nonfunctional TSHR) mice.
  • In vitro assessment of TSH and TSHR-stimulating antibody effects on primary osteoblast and osteoclast function.
  • Analysis of bone ossification, cortical and trabecular bone structure, and mineralization.

Main Results:

  • Both Pax8(-/-) and hyt/hyt mice exhibited similar skeletal abnormalities, including delayed ossification, reduced cortical bone, impaired trabecular remodeling, and decreased bone mineralization.
  • TSH and TSHR-stimulating antibodies did not elicit a cAMP response in osteoblasts or osteoclasts in vitro.
  • TSH did not influence osteoblast or osteoclast differentiation or function.

Conclusions:

  • Skeletal abnormalities in congenital hypothyroidism are independent of TSH levels.
  • The hypothalamic-pituitary-thyroid axis regulates skeletal development primarily through the action of thyroid hormone (T3).
  • TSH does not appear to directly regulate bone turnover via the TSHR in osteoblasts and osteoclasts.

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