We report a patient with
primary hypothyroidism associated with an aberrant
ACTH response to the
LH-RH test. A 40-year-old woman was admitted to our hospital displaying
headache,
nausea, and
numbness on the left side of her face, upper limbs, and
tips of her toes. Computed tomography and magnetic resonance imaging revealed a mass-like lesion in the pituitary. A high serum TSH concentration with concomitant low
thyroid hormone concentrations resulted in a diagnosis of
primary hypothyroidism. To exclude the possibility of a coexisting
pituitary tumor including a TSH-secreting
tumor, we performed dynamic TSH secretion tests. TRH testing showed an excessive, delayed TSH response, typical of
primary hypothyroidism. Serum TSH decreased not only after administration of CRH,
octreotide, or
L-DOPA, but also after administration of
LH-RH. In this case,
LH-RH testing induced
ACTH secretion. To determine if aberrant
ACTH secretion in response to
LH-RH loading is a common phenomenon in severe
primary hypothyroidism, we performed the
LH-RH test on 4 additional patients with pituitary enlargement due to
primary hypothyroidism. Two patients demonstrated aberrant
ACTH secretion in response to
LH-RH loading, but the others did not. To our knowledge, this is the first report of aberrant
LH-RH-stimulated
ACTH secretion in
primary hypothyroidism.