Signal Intensity and Volume of Pituitary and Thyroid Glands in Preterm and Term Infants

Abstract

Background: Hypothalamic-pituitary-thyroid (HPT) maturation has not been extensively evaluated using neonatal MRI, even though both structures are visualized on MRI.

Hypothesis: That signal intensity and volume of pituitary and thyroid (T) glands on MRI in neonates may be interrelated.

Study type: Retrospective.

Subjects: In all, 102 participants.

Field strength/sequence: 3.0T, T₁ -weighted pointwise encoding time reduction with radial acquisition (PETRA).

Assessment: The volume of interest of the anterior pituitary (AP), posterior pituitary (PP), and T on MRI were defined on T₁ -PETRA by two radiologists, and volumes of AP (AP_vol) and thyroid (T_vol) were calculated. Gestational age (GA), chronological age (CA), GA+CA, birth weight (BW), and thyroid function were recorded. Mean and maximum signal intensities of AP, PP, and T were normalized using signals from the pons and spinal cord as follows: signal ratio of anterior pituitary/pons (AP/pons), signal ratio of posterior pituitary/pons (PP/pons), and signal ratio of thyroid/cord (T/cord) T/cord, respectively.

Statistical tests: Correlations between signal intensity and volume measures and GA, CA, GA+CA, and BW were assessed using Pearson's correlation coefficient or Spearman's rank correlation coefficient. Thyroid function analysis and T_mean /cord, T_max /cord, and T_vol were evaluated using the Steel-Dwass test.

Results: AP_mean /pons correlated positively with GA (ρ = 0.62, P < 0.001) and BW (ρ = 0.74, P < 0.001), and negatively with CA (ρ = -0.86, P < 0.001) and GA+CA (ρ = -0.46, P < 0.001). PP_mean /pons correlated positively with GA (ρ = 0.49, P < 0.001) and BW (ρ = 0.63, P < 0.001), and negatively with CA (ρ = -0.70, P < 0.001) and GA+CA (r = -0.38, P < 0.001). T_mean /cord correlated positively with GA (ρ = 0.48, P < 0.001) and BW (ρ = 0.55, P < 0.001), and negatively with CA (ρ = -0.59, P < 0.001) and GA+CA (ρ = -0.22, P = 0.03). AP_vol correlated positively with GA (ρ = 0.68, P < 0.001) and BW (ρ = 0.73, P < 0.001), and negatively with CA (ρ = -0.72, P < 0.001). T_vol correlated positively with GA (ρ = 0.50, P < 0.001) and BW (ρ = 0.61, P < 0.001), and negatively with CA (ρ = -0.54, P < 0.001). AP_mean /pons correlated positively with T_mean /cord (ρ = 0.61, P < 0.001).

Data conclusion: Signal and volume of pituitary and thyroid glands correlated positively with GA and BW, and negatively with CA in neonates.

Level of evidence: 4 TECHNICAL EFFICACY STAGE: 5.

Keywords: PETRA; hypothalamic-pituitary-thyroid axis; pituitary gland; preterm infant; thyroid gland.