Progesterone and estrogen responsiveness to father-toddler interaction

The Family Biorhythm: Contributions of the HPA and HPG Axes to Neuroendocrine Attunement

Objective

The vast majority of research on biobehavioral influences on development has focused on mothers and infants, whereas research on paternal biobehavioral influences remains sparse. This study aims to increase understanding of paternal influences on the biobehavioral dynamics of the family unit, using a multi-system approach.

Methods

Participants consisted of 32 predominantly high-risk families recruited during pregnancy who completed monthly questionnaires and in-home visits when infants were 4, 12, and 18 months of age. In-home visits included semi-structured interaction tasks and saliva samples for cortisol and progesterone assays.

Results

Mothers and infants, but not fathers and infants, showed adrenocortical attunement, with the strongest attunement at 18 months. Second, mothers' couple satisfaction did not significantly impact infants' cortisol levels or mother-infant cortisol attunement, but mothers' progesterone moderated the relationship between couple satisfaction and infant cortisol levels such that mothers with low couple satisfaction, but high progesterone, had infants with lower cortisol levels. Finally, mothers' and fathers' progesterone levels were attuned across the time points.

Conclusions

This is some of the first evidence of the establishment of the family biorhythm and suggests that fathers play an indirect role in facilitating mother-infant adrenocortical attunement.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40750-023-00215-0.

Functional relationships between estradiol and paternal care in male red-bellied lemurs, Eulemur rubriventer

Fathers contribute substantially to infant care, yet the mechanisms facilitating paternal bonding and interactions with infants are not as well understood as they are in mothers. Several hormonal changes occur as males transition into parenthood, first in response to a partner's pregnancy, and next in response to interacting with the newborn. These changes may prepare fathers for parenting and help facilitate and maintain paternal care. Experimental studies with monkeys and rodents suggest that paternal care requires elevated estradiol levels, which increase when a male's partner is pregnant and are higher in fathers than non-fathers, but its role in the expression of paternal behaviors throughout infant development is unknown. To assess estradiol's role in paternal care, we analyzed the relationship between paternal estradiol metabolites and 1) offspring age, and 2) paternal care behavior (holding, carrying, huddling, playing, grooming), in wild, red-bellied lemurs (Eulemur rubriventer). We collected 146 fecal samples and 1597 h of behavioral data on 10 adult males who had newborn infants during the study. Estradiol metabolites increased four-fold in expectant males, and in new fathers they fluctuated and gradually decreased with time. Infant age, not paternal behavior, best predicted hormone levels in new fathers. These results suggest that hormonal changes occur in expectant males with facultative paternal care, but they do not support the hypothesis that estradiol is directly associated with the day-to-day expression of paternal care. Future research should explore estradiol's role in facilitating behaviors, including infant-directed attention and responsiveness, or preparing fathers for infant care generally.

The Role of Paternal Involvement on Behavioral Sensitive Responses and Neurobiological Activations in Fathers: A Systematic Review

As fathering research has flourished, a growing body of studies has focused on behavioral and neurobiological mechanisms, respectively associated with caregiving sensitivity and responsiveness to infant stimuli. However, the association between these aspects and the key concept of paternal involvement in childcare (i.e., contribution in infant care in terms of time, availability, and responsibility) has been poorly investigated. The current work aims to systematically review the role of involvement in childcare on both neural activations and sensitive behaviors in fathers by examining (a) how paternal involvement has been measured and (b) whether paternal involvement has been associated with neurobiological activation and behavioral sensitive responses. Inclusion criteria were peer-reviewed quantitative studies, concerning fathers responding to infant stimuli at neurobiological or behavioral level, and including a quantitative measurement of paternal involvement in childcare. A quality rating for each study has been performed based on the measurements adopted to assess paternal involvement. Of 2,529 articles, 27 studies were included. According to our quality rating, 10 out of 27 studies included fairly good-standard measures for measuring paternal involvement, whereas 17 studies used good-standard measures. In addition, 11 studies provided details of paternal involvement in the context of neurobiological responses to infant stimuli, whereas 16 addressed paternal sensitive behaviors. Overall, only 8 studies reported relevant findings about the relationship between paternal involvement and neurobiological responses or sensitive behaviors in fathers. The present study is the first systematically evaluating the scope of paternal involvement in the field of Paternal Brain and fathers' sensitive responsiveness research. When high-standard measures are used, paternal involvement seems to play a significant role in modulating both the hormonal and the neural pathways associated with paternal behaviors. Remarkably, the role of paternal engagement may underpin an adaptive nurturance that is not dependent on pregnancy and childbirth but on caregiving experience. A promising positive link between paternal involvement and behavioral sensitivity may be expected in further studies, which will need to corroborate our conclusion by adopting detailed and appropriate measures assessing paternal involvement. As a future line of research, the inclusion of gay fathers may be beneficial for the field.

Oxytocin and Human Sensitive and Protective Parenting

In this chapter we review the evidence for the role of oxytocin in parenting, and discuss some crucial but outstanding questions. This is not meant to be a comprehensive review of all studies on oxytocin and parenting in general. Instead, special attention will be paid to a dimension of parenting that has been largely neglected in behavioral and neurobiological research on parental caregiving, namely protection. Parental protection has received considerable attention in animal research but, despite its evolutionary importance, not in studies on humans. It is argued that oxytocin may have specific significance for the protective dimension of parenting. The effects of exogenous oxytocin may be dependent not only on contextual factors, but also on personal characteristics, most notably gender, on endogenous levels of oxytocin, and on early childhood experiences. Examining the contextual, personal, hormonal, neural, genetic, and behavioral mechanisms of protective parenting in tandem is essential for the development of a comprehensive theory of protective parenting, and for the identification of "biomarkers" for insensitive and unprotective parenting that should be taken into account in preventive parenting interventions.

Neural Regulation of Paternal Behavior in Mammals: Sensory, Neuroendocrine, and Experiential Influences on the Paternal Brain

Across the animal kingdom, parents in many species devote extraordinary effort toward caring for offspring, often risking their lives and exhausting limited resources. Understanding how the brain orchestrates parental care, biasing effort over the many competing demands, is an important topic in social neuroscience. In mammals, maternal care is necessary for offspring survival and is largely mediated by changes in hormones and neuropeptides that fluctuate massively during pregnancy, parturition, and lactation (e.g., progesterone, estradiol, oxytocin, and prolactin). In the relatively small number of mammalian species in which parental care by fathers enhances offspring survival and development, males also undergo endocrine changes concurrent with birth of their offspring, but on a smaller scale than females. Thus, fathers additionally rely on sensory signals from their mates, environment, and/or offspring to orchestrate paternal behavior. Males can engage in a variety of infant-directed behaviors that range from infanticide to avoidance to care; in many species, males can display all three behaviors in their lifetime. The neural plasticity that underlies such stark changes in behavior is not well understood. In this chapter we summarize current data on the neural circuitry that has been proposed to underlie paternal care in mammals, as well as sensory, neuroendocrine, and experiential influences on paternal behavior and on the underlying circuitry. We highlight some of the gaps in our current knowledge of this system and propose future directions that will enable the development of a more comprehensive understanding of the proximate control of parenting by fathers.

Hormonal systems, human social bonding, and affiliation

Which hormones are implicated in human social bonding and affiliation? And how does field research speak to this issue? We begin by laying out a broad view of how endocrine hormones in general modulate life history allocations of energy and other resources, and the ways in which their neuromodulatory functions must be understood within a broader conceptualization of how they have been shaped to affect allocations. We then turn to four specific hormones or hormone families that have received much attention: oxytocin, opioids, prolactin, and progesterone. Each plays a role in regulating psychological capacities and propensities that underlie individuals' interactions with important social targets. Yet in no case is it clear exactly what regulatory roles these hormones play. We suggest several directions for future research.

Hormonal stimulation and paternal experience influence responsiveness to infant distress vocalizations by adult male common marmosets, Callithrix jacchus

Parental experience and hormones play a large role in the common marmoset (Callithrix jacchus) father's care of their offspring. We tested the effect of exogenous estradiol or testosterone on the responsiveness of common marmosets to respond to infant distress vocalizations and whether males who haven't become fathers yet (paired males) would have increased responsiveness to infant distress calls with either steroid or whether parental experience is the most important component for the onset of paternal care. Sixteen male marmosets (8 fathers, 8 paired males) received a vehicle, low dose or high dose of estradiol and additional 16 males were tested with testosterone at three doses for their response either to a vocal control or a recording of an infant distress call for 10min. Without steroid stimulation fathers were significantly more likely to respond to the infant distress stimulus than paired males. Low dose estradiol stimulation resulted in a significant increase in fathers' behavioral response towards the infant distress stimulus but not in paired males. Fathers also showed a significant increase in infant responsiveness from the vehicle dose to the estradiol low dose treatment, but not to the estradiol high dose treatment. Testosterone treatment did not show significant differences between infant responsiveness at either dose and between fathers and paired males. We suggest that neither steroid is involved in the onset of paternal care behaviors in the marmoset but that estradiol may be involved in facilitating paternal motivation in experienced fathers.

Stress, rejection, and hormones: Cortisol and progesterone reactivity to laboratory speech and rejection tasks in women and men

Stress and social rejection have important impacts on health. Among the mechanisms implicated are hormonal systems such as the hypothalamic-pituitary-adrenal (HPA) axis, which produces cortisol in humans. Current research employs speech stressors and social rejection stressors to understand hormonal responses in a laboratory setting. However, it is not clear whether social rejection stressors elicit hormonal reactivity. In addition to cortisol, progesterone has been highlighted as a potential stress- and affiliation-related hormone in humans. In the present study, 131 participants (70 men and 61 women) were randomly assigned to be exposed to one of four conditions: standardized speech stressor; speech control; social rejection task; or a control (inclusion) version of the social rejection task. Saliva samples were collected throughout the study to measure cortisol and progesterone. As hypothesized, we found the expected increase in cortisol in the speech stressor, and we also found that the social rejection task did not increase cortisol, underscoring the divergence between unpleasant experiences and HPA axis activity. However, we did not find evidence for progesterone increase either during the speech- or social rejection tasks. Compared with past studies on progesterone and stress in humans, the present findings present a mixed picture. Future work is needed to delineate the contexts and types of manipulations which lead to progesterone increases in humans.

Stress, rejection, and hormones: Cortisol and progesterone reactivity to laboratory speech and rejection tasks in women and men

Stress and social rejection have important impacts on health. Among the mechanisms implicated are hormonal systems such as the hypothalamic-pituitary-adrenal (HPA) axis, which produces cortisol in humans. Current research employs speech stressors and social rejection stressors to understand hormonal responses in a laboratory setting. However, it is not clear whether social rejection stressors elicit hormonal reactivity. In addition to cortisol, progesterone has been highlighted as a potential stress- and affiliation-related hormone in humans. In the present study, 131 participants (70 men and 61 women) were randomly assigned to be exposed to one of four conditions: standardized speech stressor; speech control; social rejection task; or a control (inclusion) version of the social rejection task. Saliva samples were collected throughout the study to measure cortisol and progesterone. As hypothesized, we found the expected increase in cortisol in the speech stressor, and we also found that the social rejection task did not increase cortisol, underscoring the divergence between unpleasant experiences and HPA axis activity. However, we did not find evidence for progesterone increase either during the speech- or social rejection tasks. Compared with past studies on progesterone and stress in humans, the present findings present a mixed picture. Future work is needed to delineate the contexts and types of manipulations which lead to progesterone increases in humans.

PROGRESS ON THE PATERNAL BRAIN: THEORY, ANIMAL MODELS, HUMAN BRAIN RESEARCH, AND MENTAL HEALTH IMPLICATIONS

With a secure foundation in basic research across mammalian species in which fathers participate in the raising of young, novel brain-imaging approaches are outlining a set of consistent brain circuits that regulate paternal thoughts and behaviors in humans. The newest experimental paradigms include increasingly realistic baby-stimuli to provoke paternal cognitions and behaviors with coordinated hormone measures to outline brain networks that regulate motivation, reflexive caring, emotion regulation, and social brain networks with differences and similarities to those found in mothers. In this article, on the father brain, we review all brain-imaging studies on PubMed to date on the human father brain and introduce the topic with a selection of theoretical models and foundational neurohormonal research on animal models in support of the human work. We discuss potentially translatable models for the identification and treatment of paternal mood and father-child relational problems, which could improve infant mental health and developmental trajectories with potentially broad public health importance.

Salivary estradiol and testosterone in Filipino men: Diurnal patterns and relationships with adiposity

OBJECTIVES

We used detailed saliva sampling procedures to test for diurnal changes in men's salivary estradiol (E2) and testosterone (T) and assessed whether greater adiposity predicted higher E2 and T.

METHODS

We drew on a subsample of young adults enrolled in a long-running birth cohort study in Metro Cebu, Philippines. Subjects provided saliva samples at four time points during the day (waking, waking +40 min, early evening, and bedtime), which were assayed for E2 and T. Using these detailed hormonal data, we calculated E2 (n = 29) and T (n = 44) area-under-the-curve values, which provide insights on hormonal production over the study period.

RESULTS

While T declined immediately after waking and reached a nadir in the early evening, E2 did not show significant diurnal change (P ≥ 0.1) but was positively correlated to T at multiple time points (P ≤ 0.05). Subjects with higher adiposity (BMI, waist circumference, skinfolds) had elevated E2 secretion throughout the day (P ≤ 0.01), but adiposity was not related to salivary T.

CONCLUSIONS

Consistent with past research, our results indicate that adipose tissue is a significant site of E2 production in males but differ from a limited number of prior studies of young men in that we did not find lower T with increasing adiposity. Given E2's role in male hypothalamic-pituitary-gonadal function and complex interfaces with the immune system, these results have important implications for models of male life history as rates of overweight and obesity rise in populations around the world.