Table 1.

Characteristics of 86 premenopausal euthyroid women in the Michigan Polybrominated Biphenyl Registry menstrual cycle function study by thyroid hormone levels^a (2004–2014)

	N (%)	TSH (μIU/ml)	Total T4 (μg/dl)
Age (years)b
18–25	8 (9.3)	1.4	8.0
26–30	7 (8.1)	1.3	9.7
31–35	11 (12.8)	1.6	9.3
36–40	35 (40.7)	1.6	9.2
41–45	9 (10.5)	1.5	8.1
46–54	16 (18.6)	1.1	9.2
Education
High school	13 (15.3)	1.4	8.9
Some college or technical school	40 (47.1)	1.4	9.0
College graduate or more	32 (37.7)	1.5	9.1
Missing	1
Income
<$50,000/year	41 (48.2)	1.5	9.0
≥$50,000/year	44 (51.8)	1.4	9.0
Missing	1
Parity
0 prior pregnancies	19 (22.1)	1.5	8.6
1–2 prior pregnancies	28 (32.6)	1.5	9.1
3 or more prior pregnancies	39 (45.4)	1.4	9.2
Body mass index categoryc
Normal	34 (39.5)	1.6	8.8
Overweight	23 (26.7)	1.4	9.0
Obese	29 (33.7)	1.3	9.3
Smoking statusd
Never smoker	51 (59.3)	1.5	9.1
Former smoker	12 (14.0)	1.2	9.2
Current smoker	23 (26.7)	1.4	8.8
Study phase
2004–2006	30 (34.9)	1.8	9.5
2013–2014	56 (65.1)	1.3	8.8
Average behavior over study period
Weekly Exercise
0 times	28 (32.6)	1.3	9.3
1–3 times	29 (33.7)	1.6	8.8
>3 times	29 (33.7)	1.5	8.9
Stresse
Low	27 (31.4)	1.5	8.9
Moderate	32 (37.2)	1.4	8.6
High	27 (31.4)	1.4	9.6
Daily Smoking
None	63 (73.3)	1.5	9.1
1–9 cigarettes/day	12 (14.0)	1.4	9.3
≥10 cigarettes/day	11 (12.8)	1.4	8.4
Weekly alcohol consumption
0 servings	25 (29.1)	1.2	9.0
1–3 servings	42 (48.8)	1.6	9.2
≥4 servings	19 (22.1)	1.5	8.7

^aGeometric means calculated for TSH, arithmetic means calculated for total T₄

^bAge when participant started the menstrual cycle function study

^cBody mass index (kg/m²) =weight (lb)/[height (in)]² × 703 and defined as: normal: 18.5–24.9; overweight: 25.0–29.9; obese: ≥30.0

^dBased on the questionnaire responses and daily diaries during the study

^eStress determination is based on a combination of duration and intensity