Management of Central Hypothyroidism

Diagnosis and Evaluation

Low TSH with low free T4 is the classic pattern of central hypothyroidism, indicating pituitary or hypothalamic dysfunction 1
Morning ACTH and cortisol levels can be used to evaluate pituitary function, and gonadal hormones (FSH, LH, testosterone/estradiol) can also be assessed 1
An MRI of the pituitary may be considered if not previously done, to evaluate pituitary function 1
Evaluation of other pituitary hormones is necessary, as central hypothyroidism can be associated with other hormonal deficiencies 2

The American College of Endocrinology recommends titrating levothyroxine dose based on free T4 levels, not TSH, in patients with central hypothyroidism 1
The goal is to restore free T4 to the upper half of normal range in central hypothyroidism, with a standard replacement dose of 1.6 mcg/kg/day in younger patients without cardiac disease 3
In elderly patients or those with cardiac disease, lower starting doses of 25-50 mcg are recommended 3
Dose adjustments should be made in 12.5-25 mcg increments every 6-8 weeks until optimal free T4 levels are achieved, with monitoring every 6-12 months or with symptom changes 4

Free T4 is the primary monitoring parameter in central hypothyroidism, as TSH is unreliable, and the goal is to maintain free T4 in the upper half of the normal range 1
Thyroid function tests should be monitored every 6-12 months once stable, and rechecked 6-8 weeks after dose adjustments 3
If central hypothyroidism is confirmed, other pituitary hormones should be evaluated periodically 2