Central Hypothyroidism

Abstract

Identify the causes and pathogenetic mechanisms underlying acquired, congenital, and transient central hypothyroidism (CH). • Describe the clinical and endocrinological characteristics of CH. • Recall the most effective treatment of CH, the best marker of treatment response, and the perils of undertreatment and overtreatment. Most patients with hypothyroidism have thyroid failure or primary hypothyroidism. Central hypothyroidism (CH) is caused by impaired stimulation of a normal thyroid gland by hypothalamic or pituitary hormones. Most cases of CH are caused by pituitary tumors, but genetic defects causing abnormalities in the thyroid-stimulating hormone (TSH) ␤ subunit also lead to CH. The symptoms are similar to those of primary hypothyroidism, and most patients with CH will also have signs and symptoms of other anterior pituitary dysfunction. The diagnosis of CH can be missed if a TSH is the only screening test used for detection of thyroid disease, and we recommend measurement of both free thyroxine and TSH for screening purposes. The treatment is the same as in primary hypothyroidism except that TSH cannot be used to monitor therapy. It is important to assess the pituitary adrenal axis before starting levothyroxine to avoid precipitation of adrenal crisis in patients with adrenal insufficiency. ■

Central hypothyroidism

“…Children may present with short stature, failure to thrive or delayed skeletal maturation, which may also denote underlying concomitant GH deficiency. [ 47 ] If TSH deficiency is suspected, measurements of GH and cortisol may indicate panhypopituitarism. The presence of hypoglycemia in a term neonate should suggest GH and/or adrenocorticotrophic deficiency.…”

“…[ 66 ] Bradycardia, hypothermia, slow speech and delayed relaxation of deep tendon reflexes may be present. [ 47 ] The occurrence of TSH deficiency occurs usually after loss of GH and gonadotropin secretion in patients with secondary hypothyroidism. Features of other pituitary hormone insufficiencies such as amenorrhea, infertility, hypoglycemia, anorexia, weight loss and diabetes insipidus may be seen.…”

“…Appropriate neuroimaging such as magnetic resonance imaging of the pituitary gland and, less commonly, computed tomography should be employed to help identify any mass lesion as a possible cause. [ 47 ]…”