Table 5.

Correlations Between Thyroid Hormone Levels and Cognitive Measures in LT4 Treated Subjects

		fT4		fT3		TSH
	Test	Coefficient	p-Value	Coefficient	p-Value	Coefficient	p-Value
Declarative memory	Paragraph Recall Test
	Immediate	1.07	0.20	−0.005	0.93	0.19	0.38
	30 min delay	0.89	0.31	0.02	0.71	0.20	0.40
Executive function	Letter Cancellation Test
	Time (sec)	−4.97	0.33	−0.04	0.90	2.04	0.13
	% with no errors	15%	0.81	−8%	0.13	5%	0.77
	Trail Making Test
	Time (sec)	1.67	0.40	0.26	0.05	0.31	0.56
	ABC time (sec)	−0.54	0.92	0.08	0.83	−1.04	0.46
	% with errors	−23%	0.72	1%	0.82	25%	0.27
	% with ABC errors	−41%	0.32	6%	0.17	−14%	0.33
	Iowa Gambling Task
	Net-1	0.04	0.99	−0.03	0.88	1.65	0.02
	Net-2	−1.68	0.50	0.08	0.63	−0.44	0.50
	Net-3	−1.46	0.59	−0.07	0.71	0.25	0.73
	Net-4	−0.94	0.75	0.02	0.94	−1.05	0.17
	Net-5	−2.10	0.48	−0.09	0.67	−1.11	0.16
Executive function (working memory)	N-Back
	No. correct on target
	1-Backa	66%	0.38	−6%	0.13	24%	0.20
	2-Backa	−9%	0.84	0.5%	0.90	16%	0.29
	3-Back	−0.27	0.66	0.01	0.77	−0.18	0.30
	N-Back
	No. incorrect/nontarget
	1-Backa	−66%	0.08	3%	0.56	–30%	0.05
	2-Backa	6%	0.92	−1%	0.82	−8%	0.59
	3-Back	–1.05	0.04	−0.03	0.37	0.004	0.98
	Subject Ordered Pointing
	No. of errors
	6	0.11	0.32	0.001	0.85	−0.02	0.50
	8	−0.04	0.83	−0.002	0.90	−0.0004	0.99
	10	0.17	0.46	−0.001	0.94	0.03	0.67
	12	−0.12	0.70	0.01	0.73	−0.06	0.43
Motor learning	Pursuit Rotor Trial
	Time on target (sec)
	1	0.52	0.88	0.05	0.83	−0.09	0.93
	2	1.74	0.60	0.01	0.96	0.41	0.65
	3	0.04	0.99	0.07	0.77	−0.18	0.85
	4	3.03	0.37	−0.16	0.49	−0.04	0.97
	Motor Sequence Learning Test
	Total movement time (sec)	−59.05	0.45	7.20	0.16	−2.49	0.90

Individual tests are grouped by cognitive subdomains (first column).

Correlations were analyzed by repeated measures methodology using separate models for each hormone.

Positive coefficients indicate that the measure increased with increasing hormone levels, while negative coefficients indicate that the measure decreased with increasing hormone levels.

For continuous cognitive measures, the magnitude of the coefficient indicates the estimated change in the measure with a 1 unit increase in fT4 or TSH, or a 10 unit increase in fT3.

For binary cognitive measures, coefficients were transformed to estimate the percent change in the predicted odds of the measure for a 1 unit increase in fT4 or TSH, or a 10 unit increase in fT3. The transformed coefficients are estimates of the risk ratios associated with the 1 or 10 unit increase in the respective hormone level.

p-Values for continuous outcomes were adjusted for age, years of education, WAIS-R, BMI, estrogen status, LT4 time, LT4 dose time, and LT4 dose (μg/kg). Significant coefficients are shown in bold with corresponding p-values.

^aThese values were calculated as proportion of subjects for which each measure was ≥15 (for correct target) or >0 (for incorrect/nontarget), since there were floor effects. The N-Back p-values for comparing groups do not include 3-Back since this variable was not calculated as a proportion.